Six off one,half dozen of the other.
The EoTech (551/552 and 511/512) were made to mount directly to the upper receiver's rail and achieve true co-witness. The Aimpoint would require a seperate mounting ring made for co-witnessing, and because of the rear sight's consruction, it should probably be a forward canting/cantilever mount that will mount onto the receiver but put the Aimpoint partially over the hand guard.
Steve/RRA