The repro's are junk, but they do look good for a while and they are cheap. If your low on cash buy the repro, if you want a nice bumper and you have the dough have yours rechromed.
That varies greatly and so does the quality, the best I can suggest is to ask around the local car clubs for someone in your area that does a nice job and get a quote.
In the past I have purchased the repros only to have rust show up within a year. This time I had mine rechromed for $140 ea. I would not call it a "show car" finish but it is better than the repros. I later found someone who would give it a "show car" finish for $269 ea. I would have spent the extra money had I known.
Powder coating would be pretty cheap. The place I use would probably do it for $20 each or so.
I recently got a quote from a very high-end chrome shop for about $300 each to do the bumpers. This is for absolutely perfect chrome though.
In my experience, the repro bumpers from Dynacorn are the best of the repros. I have purchased several for project cars and have been pleased. I get them from K.A.R. Auto Group (www.karmustang.com).