I only say easy to find ammunition because my buddy has a rough time getting ammunition for his .270 and I have an even harder time finding quality 22-250 ammo. I'm not saying i'm taking 1000 yard shots every day I just like the ability to be able to try it. That being all said I think I'm going to go with 7mm as I keep hearing good things about it.
7rem is a good choice, what rifles are you looking at? Do you reload?