If you are dealing with egg whites, you need a good whisk (except for the lazy people, like me, who use mixers). Though, truth be told, sometimes I'm too lazy to clean the mixer for a small job and I find myself reaching for the whisk.
I like the OXO 9-in. Good Grips Egg Whisk. It has a nice gripping handle. So, I don't need to grip with as much force to keep a hold of it and my hand doesn't get as tired.
If you have a small job that you just need to knock out quickly, a whisk is a good choice. For larger jobs, you probably want a mixer (unless you are trying to impress someone).