Depends on a couple of things. First off, what type of area are you hunting to have a limitation of 50-150 yards? Do you reload? As for money, what are you willing to spend? A .223 is a good starter rifle with cheaper ammo out there that will do the job, provided you produce a good shot. The .204 Ruger is a excellent round, smaller of course than the .223, and a little more expensive if you do not reload. Yet, the .204 is a very quick, accurate, and easy round to work with. Then you can go on, 22-250, .243 all the way up to my favorite rounds, .308 and .338 Lapua. Yes, you can have nice pelts with both of the .30 calibers, but the Lapua does have a knack for a thumper of a recoil.. Anyways, if you stick with the .20 calibers, .204 is my vote. .223 would be cheaper in ammo in the long run, but if you are not shooting 100 rounds a weekend, my vote is for the .204. I shoot a .204, the .308 and the .338 Lapua for all my yote hunting, and I pelt out everything I can, unless the dogs are mangy or loaded with parasites. And if I am feeling frisky, I take my bows with me as well....I have had some great mornings with my Hoyts.

p.s. I would do some thinking on the caliber first, then the manufacturer and any add ons. Plenty of great manufacturers out there, but don't go for the sale item that is just ok. A yote gun is just as important as the elk, bear, or even deer rifle. Put some money, without taking a loan, into a scope as well as some good calls, camo, and other necessary gear. It will all add up on a nicely to take that pesky yote.