I buy both reps and gens. The 21j reps are fun for me because I have no worries - I consider them semi disposable.
For example, I have a gen Omega 300m and rep Omega 300m. It's perfect for me to have both because I can go to the beach, park, work in the yard etc... and wear the rep of a watch I love.
I am very happy with the reps I buy. There are quality differences, of course, between the reps and gens (pearl, lume, dial, hands, screw down crown, etc..., etc...), but from a foot away you probably couldn't tell the difference between a good rep and a gen.
I'm very happy with both, as they serve different purposes for me.