Good ones guarantee perfect alignment so you don't have to hone. However, I've never had to hone quality rings on a one piece base, so I'm not sure how important that is.

Some one piece mounts drastically limit fore-aft adjustment. I passed on a Spuhr for exactly that reason on my bolt gun. As much as I like the idea of one piece mounts and Spuhr in particular, I think rings are the answer for a bolt gun.