If you're referring to firmware, there have been no major changes to firmware since BFB297... 301-305 or 307 is simply BFB297 with a few bug fixes. Just make sure you get 297 or higher and not 251.

If you're talking about body styles, who knows. There are 5R's, 5RA's, 5RE's, 5RA+'s, 5RII's, and any number of others... all of which are the same radio with a few cosmetic differences.

I recommend either this vendor ( http://www.ebay.com/itm/BaoFeng-UV-5...item2a2f44cca9 ) or Three Old Crows General Store. Both of these vendors are excellent and have excellent customer service.