Lol at some of you silly people even if you think pain would win low-mid difficulty? Lol just silly...but that's your opinion
Imo itachi would win (not easily), but yes pain has a lot of op techs but so does itachi and on top of that itachi has shown the brains to over come op techs....but all we get from pain is power not brains (if I'm wrong tell me), and imo that's not enough to beat someone with power and brains
Classic examples: naruto and Neji, Shikamaru and hidan, sasuke and dedara, hell tom and jerry lol you get the point.
So in more cases than not brains + power > power alone and that's fact
Also to all those (the op) saying that kabuto was controlling pain when he got beat (sealed) kabuto was also controlling him when he was beating up naruto and bee, 2 tail beast host...on top of that they are the 8 and 9 tails the most powerful of the beast....so kabuto did a great job controlling him, don't take away from kabuto its not his fault. The problem is itachi is just a force to be reckoned with and that's all. Pain was used flawlessly but itachi found all the holes in pain's techs end of story (which is y I think itachi would win)
Uchiha out