Anyone who compares a gen with a rep is deluded. There is no comparison. Maybe when you're talking about Tag Heuer, but when we're talking about AP, Panerai, IWC, Rolex etc. - the gen is so much nicer and more satisfying.
However, a rep is an excellent way to tell whether you like a particular style. I think if you appreciate a brand, you ought to buy the real thing. Do unto others as you would have others do to you. Would you like anyone to rip your job off, and undercut you by doing what you do at a lower price? What goes around comes around.
However there are just so many brands out there, and reps are a good way to sample them. They also make good beaters. Those are my two reasons for buying reps: sampling, and using them as beaters. For horological appreciation - only a gen will do.