This is a bit of a tough question that I'm sure many people have to mull over for quite some time. First and foremost my suggestion is being cognizant of the nuances of each rep, and understand that differences in brand, model and the rep factory you're getting the rep from play a large part not just in the movement under the hood, but also the look. Different factories product minutely different iterations of the 'same watch' from one another, and even over time the same factory may slightly improve the look (take Clean's GMT Master II BLNR V2 that CTime posted about within the last week).
Movement of course plays a large role in what you choose. The more money you spend on a 'closer' clone movement, the closer the overall feel is to a gen article but depending on what you're going for, there still may not be that perfect 1:1 you may be looking for. Nice example, again, being for the GMT Master II's and the newly release DD3285 movement. Prior to this release I believe (may be wrong) but we were relying on 3125 movements, just with 3285 markings instead. This is for a terribly popular watch and a movement that I think was released 5 years ago. Depending on the brand and the age of the model you're after, there may be an even bigger difference between current top-end rep movement and gen movements.
Tangentially related to this is your other question about repairs. From my understanding there is a growing number of decent to excellent watch-smiths/watch repair services for the rep community/market. I am not too knowledgeable on this at the moment, but there is some genuine hope to be had that if your watch breaks down you can get it repaired by someone with the required knowledge, skills, and willingness. Movement accuracy to source material and whether a given rep movement can house gen parts is also something to consider, if you fancy that. I can't speak to how expensive it is to repair these reps, but having dealt with having to repair my own gen articles, I'd like to think here too the rep market is relatively cheaper than repairing gen. Maybe not always as easily sourced, I'm unsure. But the market is there, and it seems as if savvy watch-smiths have picked up on that.
So.. in short, read up on the particular rep you're after, compare different factories and movements if applicable. Be aware that repairing isn't impossible, but don't fool yourself into thinking that a rep (that are not as meticulously put together as gen) will give out at the same time as a gen and need some servicing at similar intervals.
Depending on your situation, it may be worth it to buy a 'superfranken' or something from this forum, that features a lot of high quality gen parts, has recently been taken care of and serviced by a previously loving owner. Or perhaps by yourself a "run-of-the-mill" rep from a TD and find a willing and skilled smith to get it proofed, cleaned, make sure it's starting off its life on your wrist on the right foot.
In my opinion the major draw to gen articles at this point is appreciation (resale value), and ease of repairs (don't have to look high and low for a rep repair artist). You don't have to try as hard to get it serviced, and if you're into tried and true models of steel Rolex, it'll be worth more on your wrist in 5-10 years than it is today. If you're going for the look, similar feel, and don't mind a bit of extra research and work on your part, you can get a rep for 1/10th of the cost or more. Depending, of course.