I'll chime in on this one. My opinions are based on countless discussions with a friend who worked in a chrome shop for a number of years and then opened his own polishing shop where he does show quality trim straightening and polishing of stainless steel trim.

Chrome, pros:
Luster: chrome shine has an unmatched depth to it
Color: chrome has a slight blueish tint to it
Chrome cons:
If you bend it or scratch it you are done. Want it fixed? Send it back to the shop to have all of the chrome ground off, straighten the piece and re chrome.
If damage occurs that breaks through the chrome and nickel layers the underlying steel will begin to rust and the chrome will peel off.

Stainless cons:
doesn't have that blueish tint, however it also doesn't have the yellow of nickel, I would call it color neutral.
Possibly a bit less depth of shine, I really can't describe this without pointing to a piece of chrome next to a piece of polished stainless. 99.9 percent of car nuts will never know the difference.
Stainless pros:
Got a scuff or scratch without a dent.? Get out the sandpaper and polishing compound and take it out in the same manner hat you buff out paint. A lot harder surface and you probably start with a more aggressive grit but the concept is the same.
Bend or dent? The chrome/polishing shop can fix it just like they did with the chrome bumper but without the labor of grinding off the existing chrome or the expense of replating it. As he EPA gets increasingly out of control chrome plating is likely to become prohibitively expensive or shut down entirely.

With all of that said I have not seen any examples of stainless bumpers and I would expect that out of the box they will not have a show quality shine, but here again, get out the polishing compound and buff it out.

I hope that someone finds this helpful.

40 chevy 1.5 ton, 50 chevy 3/4 ton, 67 chevy stepside 1/2 ton, 67 C50, 68 C50, 73 chevy 4x4 3/4 ton, 2004 Silverado 1/2 ton , 2005 HD 3/4 4x4 Duramax (don't even get me started about my Oldsmobiles!)