Problem with the rolex sub is that 99% of the population has never really held one or examined one in the first place. Upon inspection the gen sub would not appear all that great to many (hollow links, ect.) If you handed a gen rolex to the same people that say your rep is fake they would still say the gen is fake. The real test is if they can tell you why/how its a rep.
My daily wear/beater watch is a gen omega smp, and my wife has held it a few times, i handed her the rolex at the ad... and she thought it was junk. She did say my rep lv felt and looked like the same "junk" as the store... not sure if thats good or bad, but to each his own.
If you get something like the breitling, zenith, or even IWC (even though its extremely expensive 99.9% of the populations doesnt know that) you'll rarely if ever get questioned if its real. Rolex most people assume its fake unless they believe you would and could actually buy one.