Best bet is just to watch some gameplay footage of both games on YouTube and see which one appeals more to you. I personally prefer RE6, but that's because it's a fun game to play even on single player. ORC is purely intended for online use, offline it's terrible.
I didn't really get into ORC, and the campaign is way shorter than RE6. the online versus is the main focus of the game rather than the campaign. so if you're into competitive shooters and have friends who play ORC, you may enjoy it. but if you're going to play it by yourself and want it for a good story mode, you should skip it and go with RE6