Highly unlikely it will matter, it's luck of the draw. You're just as likely to get a good 6800k as you are a 6850k. There will be good silicon and bad silicon for both. and since their stock clocks are both so conservative it's not like they are actually bothering to bin them, there would be little reason to.
Do they not bin them even cause of the 40/28 PCI-E lane thing? Or do all the CPUs come by default as 40 lane, then Intel basically "degrades" them into 28 lane parts to create 28 lane 6800k´s?