As a noob myself, it has taken me a while to get my head around the different movements available for watches, I could not find a 'beginners' thread with this info all in one place, so here is my summary to (hopefully) help other noobs. If there is interest, I will update it as my knowledge increases - please let me know if I have made any glaring errors or omissions, or put it in the wrong place, but remember, I have tried to keep it simple and this is new to me too!
Quality Control
Although the Chinese movements are generally well made and assembled, the same does not go for how the watches are assembled, they are often very dirty inside, and poorly lubricated. There is very little if any QC, and whichever movement you get, there is a fair chance that it will not work properly. I have heard a 25% fail rate is common, some people are even more unlucky. Dealers usually do not check before shipping, even if they claim to.
1) Quartz
This movement (in reps) is often used in chronos. Accurate timekeeping, reliable, and is the only commonplace option for a working chronograph other than the 7750. Although many non-chrono gens have quartz movements, with some brands (eg. Omega), you will be hard pushed to find many non-chrono reps that do, in other brands they are more common, eg. Tag Colt, Tag Tiger Woods golf watch, Chanel J12, Cartier. They seem to be more common in ladies' watches. Check the photos carefully before buying a quartz rep, often they are not very good quality (but the examples here tend to be good).
Drawbacks: if in a watch that is a copy of an auto chrono, the subdials are often switched into the wrong positions, and the scale can be wrong - eg. 6-12-18-24 marks instead of 3-6-9-12. Also with some exceptions (eg. Tag Indy 500) they 'tick' only once per second, so you don't get the smooth sweeping second hand of an auto.
2) Swiss ETA
ETA is a Swiss company owned by Swatch. They have supplied movements to may gen manufacturers, so if your rep has an ETA it may be almost identical to the gen. Note: ETA produces movements in Asia as well as Switzerland, but as these are in ETA factories to ETA standards, they are generally all referred to as 'Swiss'.
Drawbacks: ETA have had problems with supply, and have slowed supply of their movements to third parties, particularly in Asia. Beware if you buy a watch advertised as having a 'gen Swiss ETA' it may be a reconditioned movement, or even just an Asian clone.
3) Asian 21J
This is a workhorse movement, usually the cheapest option. Biggest difference from higher-end movements is the speed - 21Js usually have about 6 'ticks' of the second hand per second, as they have a 'low beat' at 21,600vph. Many gens have a 'high beat' movement with about 8 ticks per second (28800 vps). This can be the biggest 'tell' in a 21J powered rep.
Subject to the same QC comments above, they are generally solid and reliable.
A big benefit is that if it breaks, it is cheap to replace the entire movement, or even just replace the watch. Unless you are going to have a go yourself, it is usually not economical to repair.
Note: Many chronograph watches are available with a 21J movement. These are not chronos - the big second hand will just sweep, and the subdials just count off minutes and hours. Often referred to by dealers as 'military time' dials.
4) Asian clones
Copies of ETA movements, eg 2824 and 2836, etc. Getting better all the time, and almost identical to the ETAs. Usually a better choice than 'Swiss ETAs' (you may just get a clone anyway).
Avoid the clone 'Asian 3135' movement, sold as a Rolex clone. It is a waste of money.
5) Handwind movements
There are two common ones I am aware of, the Sea-Gull 'Lemania' as used in the display-back moonwatch, and the 6497, as often used in the Panerai reps.
They are both considered good movements, and if you get the 'swan neck dagger with Incablock' in the 6497 then it will be almost indistinguishable from the gen (whatever that means..!)
6) Asian 7750
If you want a working chrono, your choices will usually be a 7750 or a quartz.
Asian copies are getting better, but have had problems in the past. They can be expensive to service (c. $250?). They were originally designed for 12-9-6 layout dials, apparently the adaptation for 'seconds at 3' works ok, so they can be used in 'tricompax' 3-6-9 watches, although the changes mean that the datewheel is lower, giving the 'sunken datewheel' issue.
Avoid any 7750 watch with 'seconds subdial at 6' - such as some Daytona models. Apparently it uses about *14* gears to drive the seconds hand, a bit of a bodge and usually gives problems, so avoid them.
So thats the sum of my knowledge so far - I hope it helps someone, and sorry if there is any duff information - I have only been into this for a few weeks so please have patience, and let me know so I can correct it...!
Quality Control
Although the Chinese movements are generally well made and assembled, the same does not go for how the watches are assembled, they are often very dirty inside, and poorly lubricated. There is very little if any QC, and whichever movement you get, there is a fair chance that it will not work properly. I have heard a 25% fail rate is common, some people are even more unlucky. Dealers usually do not check before shipping, even if they claim to.
1) Quartz
This movement (in reps) is often used in chronos. Accurate timekeeping, reliable, and is the only commonplace option for a working chronograph other than the 7750. Although many non-chrono gens have quartz movements, with some brands (eg. Omega), you will be hard pushed to find many non-chrono reps that do, in other brands they are more common, eg. Tag Colt, Tag Tiger Woods golf watch, Chanel J12, Cartier. They seem to be more common in ladies' watches. Check the photos carefully before buying a quartz rep, often they are not very good quality (but the examples here tend to be good).
Drawbacks: if in a watch that is a copy of an auto chrono, the subdials are often switched into the wrong positions, and the scale can be wrong - eg. 6-12-18-24 marks instead of 3-6-9-12. Also with some exceptions (eg. Tag Indy 500) they 'tick' only once per second, so you don't get the smooth sweeping second hand of an auto.
2) Swiss ETA
ETA is a Swiss company owned by Swatch. They have supplied movements to may gen manufacturers, so if your rep has an ETA it may be almost identical to the gen. Note: ETA produces movements in Asia as well as Switzerland, but as these are in ETA factories to ETA standards, they are generally all referred to as 'Swiss'.
Drawbacks: ETA have had problems with supply, and have slowed supply of their movements to third parties, particularly in Asia. Beware if you buy a watch advertised as having a 'gen Swiss ETA' it may be a reconditioned movement, or even just an Asian clone.
3) Asian 21J
This is a workhorse movement, usually the cheapest option. Biggest difference from higher-end movements is the speed - 21Js usually have about 6 'ticks' of the second hand per second, as they have a 'low beat' at 21,600vph. Many gens have a 'high beat' movement with about 8 ticks per second (28800 vps). This can be the biggest 'tell' in a 21J powered rep.
Subject to the same QC comments above, they are generally solid and reliable.
A big benefit is that if it breaks, it is cheap to replace the entire movement, or even just replace the watch. Unless you are going to have a go yourself, it is usually not economical to repair.
Note: Many chronograph watches are available with a 21J movement. These are not chronos - the big second hand will just sweep, and the subdials just count off minutes and hours. Often referred to by dealers as 'military time' dials.
4) Asian clones
Copies of ETA movements, eg 2824 and 2836, etc. Getting better all the time, and almost identical to the ETAs. Usually a better choice than 'Swiss ETAs' (you may just get a clone anyway).
Avoid the clone 'Asian 3135' movement, sold as a Rolex clone. It is a waste of money.
5) Handwind movements
There are two common ones I am aware of, the Sea-Gull 'Lemania' as used in the display-back moonwatch, and the 6497, as often used in the Panerai reps.
They are both considered good movements, and if you get the 'swan neck dagger with Incablock' in the 6497 then it will be almost indistinguishable from the gen (whatever that means..!)
6) Asian 7750
If you want a working chrono, your choices will usually be a 7750 or a quartz.
Asian copies are getting better, but have had problems in the past. They can be expensive to service (c. $250?). They were originally designed for 12-9-6 layout dials, apparently the adaptation for 'seconds at 3' works ok, so they can be used in 'tricompax' 3-6-9 watches, although the changes mean that the datewheel is lower, giving the 'sunken datewheel' issue.
Avoid any 7750 watch with 'seconds subdial at 6' - such as some Daytona models. Apparently it uses about *14* gears to drive the seconds hand, a bit of a bodge and usually gives problems, so avoid them.
So thats the sum of my knowledge so far - I hope it helps someone, and sorry if there is any duff information - I have only been into this for a few weeks so please have patience, and let me know so I can correct it...!