From personal experience working on laptops for 4 years now, the i3 is pretty bad, I dont care what those reviews say, its the modern day Celaron compared to everything out there.
Core i5, even the lowest end is miles ahead of the i3, core i5 is one of the best Gaming CPU's types on the market, quite good for laptops because dual cores are technically more efficient then quadcores in laptops in real life wear and tear.
Quadcore AMD is very nice, the prices AMD has for quadcores are very attractive and iv yet to have any kind of sluggishness on quadcore AMD's very snappy very cheep.