I had this same debate with my hunting friend just the other day while out looking for some chickens.
But the debate ended when we started talking about cost. I can reload for my .243 for about 35 cents a round with a V-max 65 grain bullet on Varget powder and "pip the ace" every time.
.17 ammo is what? 15 dollars for a box of 50. That's 30 cents a shot.
If the boom isn't a factor and you reload. Go for a accurate centre fire rifle. 223, 22-250, 222, 204, 25-06, 243. You can make some pretty amazing varmint rounds for any one of these.
But, with that said a .17 hmr is very accurate and bullets are readily available so if the boom is a factor and you don't reload go with the 17hmr. I can only think of one place here that sells the Mach2 but there are several with the hmr.