I've found that I tend to buy camo according to what type of hunting I'm using it for and personal preferences. For me, considerations often include the below list. It's pretty rare, however, that a single piece of camo clothing piece will have all of these qualities. Generally, I find myself making compromises depending on what's more important for the hunt that day.
1. Terrain--does the camo pattern match or stick out and draw attention?
2. Warm or cold weather--I usually have to deal with both so purchase accordingly.
3. Burr resistant--Deer and bear hunting usually means lots of burrs. I like pants that shed burrs but am considering some chaps as another solution.
4. Waterproof--Sometimes it's needed, most times it's not.
5. Quiet--This usually means cotton for me which is a lot more comfortable.
6. Cost, Quality, where it's made--Quality usually involves more cost (not always) and made in the USA sometimes (sometimes not) involves more cost. I've found that made in the USA usually comes with better quality.