in that price range the only difference between an "i3" and an "i5" is turbo boost, and i think some i3's don't have virtualization support. Intel revamped is product naming schemes to supposedly simplify things but it's made it more complicated than ever and its mostly just marking buzz.
go with whatever fits your budget and don't feel like you should spend more just to get an i5, its not worth it.
http://www.intel.com/products/proces...ifications.htm
http://www.intel.com/products/proces...ifications.htm
same cache, same speed, same power consumption, both have HT.