I have a CTK AI bipod on an AIAT. It is pretty crude the way you cut away the stock sides and the fact that it sticks below the bottom of the stock when fully retracted.
I also have a BT-12 on a Magpul PRS stock. I like the way it folds and rides on a bag when collapsed. The locking and adjustment is better than the CTK.
Based on on the images, I would much rather have the folding retraction, secure adjustment and finished look of the BT 57.
That being said, I don't use either monopod. I prefer the faster more fine adjustability and smoother recoil when using a rear bag.