There are advantages and drawbacks to both.
In my experience the Harris is more rigid and stable than the Stoney Point. The Harris is heavier and mounted to your rifle. THis provides more of a solid rest when deployed but also is somewhat cumbersome for an off hand shot, should one be presented. The Harris once set in place also will not allow much of a pan before repositioning the legs, as they do not swivel left and right.
The Stoney Point is not hard mounted, so to speak, and can be carried seperately and then popped on when needed. This works great for the stalking we do, as is often the case, we end up jumping the game at close qaurters. The attachment is simple and quick as it simply pops onto a pre mounted fixture on the forearm of your rifle. It hasn't been a noticable hinderence in any hunting situation I have used it yet. The S-P allows you to follow moving game if your wating for the right shot, as it will allow you to pan left or right to a decent extent before having to reposition the legs.
The drawback that I have experienced with the S-P is that they are pretty flexible as far as when your spreading them out. THey also swivel easily and you have to manually set the twist locks on the legs when you deploy them. This takes extra time that sometimes you really do not have. Where the Harris are basically just pull set and your ready. If your in a situation where you can get set up to cover an area or are not rushed the S-P's can be used effectively. You could also set the legs out and lock them in advance to allow a faster set up time.
I would say that either can be decent out to 500yds, with practice. It would just depend on how you hunt and what your looking for in the rest. The Harris is a more solid fixture, but the S-P is more versital in some situations.
I use the S-P on a Compact Ruger 308 and a 7# Rem in .270 Win. The Harris are used on a Sendero in 7mag , 25/06, and now my .270 AM. All have made shots on game out to 400yds, but for the precise work I generally am using the Harris.
