Need help with my 3rd base position?

Right now i have polanco filling in there cause my original guy was zimmerman, i was thinking about liking up jhonny peralta, peralta has been hot of late, but polanco has a better average, i was also thinking tht polanco would get better rbi's cause of the team he plays for but not sure, so was just seeing some other opinions, should i pick up peralta or keep polanco