That also comes in the same package. Comes down to user preference, compare the two in terms of memory and peripherals, I thought the 328 had more to offer in that tiny package, but it's been awhile. I have successfully used that 4x4mm Atmega328 on a project. I of course didn't solder it, one of the tech's I worked with did, he probably heatgunned it, hand soldering something like that could be miserable if you are new to soldering, heatgun or reflow is your best option there. Watch Ben's reflow oven episode to make your own, that thing is pretty sweet when it's in action, though leaded solder smells a bit :-)
