Voted Cesc. Not that i disrespect Villa, but the central midfield has always been completely integral to our tactical approach and thus success. Its weakening recently, due to Iniestas injury proness and Xavis aging (i.e. seemingly needing more rest already this season) and there is hardly any proven replacement available currently. I also believe that Cesc has to be in Barcelona at least for 2 years to take over Xavis role w/out any loss.
Villa might be a big success on the left flank, but its still not his favored position id guess ... unless they switch the tactics permanently into a 2-striker + trequartista (messi) system. But then there is still Bojan, who would have no bright future anymore in Barcelona id guess.
Thats why id rather get Cesc and rotate between left wingers among Pedro, Iniesta and a fresh face with a rather comfortable price tag (max 15-20M), who is also a specialist for his position. I dont see more than one 30+M transfer next summer anyway.