Breitling, Rolex, Omega and PAM are the most popular brands so obviously there are more high quality reps of those.
I have no favourite brand _to collect_. I'm always looking for variation. I'd like to see more good quality reps of fine brands like Zenith, TAG, Tudor and Ebel.
Why no decent rep of Zenith El Primero for example, the mother of all mechanical chronographs? Or TAG Aquagraph/Aquaracer 2000 Chronograph... or Tudor Submariner? I'm still waiting.
I'm pretty sure I'm completely done with Rolex. GMT and vintage Sub are the only models that I always wanted... and I have them.
I always try go for models that are convincing and not too "overboard". Like Daytona: I really like the looks of the modern Daytona but I don't want to wear a rep of a $10K watch. Probably 19 out of 20 Daytonas out there are fakes. Unfortunately the statistics for Submariner are very similar.