I hope my new guy comments dont come off as a know it all type thing, but I am kind of a gun nut and am always looking for equipment that meets my needs.
Here are my observations:
A bi-pod is great for sitting on a hill and taking shots at targets in front of you (like prairie dogs), but its range of motion is limited in the sense that it limits the effective area covered by your rifle by panning from left to right. So you have to pick up the rifle and re adjust if you are trying to shoot outside of the angles it provides. One thing I like about them is that it really is a stable platform for quick shooting. One thing I dont like is that it makes a rifle heavy in the front end and really throws it off balance, which makes for a difficult off-hand shot.
Shooting Sticks really provide a fair amount of versatility and freedom when taking a shot that you need stability with, but can be cumbersome to carry.
My other point to consider is quality. I have two friends that both went on the cheaper side for a bi-pod and for shooting sticks. Both of them broke the first day they used them. I learned from them and bought a Harris Bi-Pod and have never had a problem with it (BTW it doesnt swivel, and I dont think it was worth the extra money). And with the shooting sticks, after seeing my buddy fidget with them for a few minutes, I decided that it just wasnt worth the frustration for me personally.