Picatinny rails are great for attaching all sorts of cool stuff to your gun bi-pods, flashlight lasers ect...
Arca rails are to the camera world what the Picatinny rails are to the gun world.
Picatinny rail for the bi-pod
Arca rail for the tripod right
Arca rail for the tripod left.
A closer look at the K&L Picatinny Trigger Guard Replacement Arca Rail. It has a T-Rail so you can slide an Arca Rail Adapter right on and have the best of both worlds.
This is the Gen 2 model I like it because you can get the Arca rail set back further as it balances the gun on a tripod much better. This is a big plus for tripod mounting.
Near the opposite is true for bi-pods as you want to mount them forward near as far as you can get them.
Hopefully this will give you some kind of an idea when you look at the others what their limits might be.
The K&L and Saber Tactical units are all very nice from what I can tell. Some of the units will balance on a tripod better and others will handle a bi-pod better.