Ok,
So I'm new to AR's with optics.  I'm planning my Sept.14th rifle.  It's going to be a 14.5" LMT M4 Upper with LMT BUIS and RASII.  I'm most likely going to go with an Aimpoint (but still thinking maybe on an EOTech).  Now, I assume that most people prefer the Aimpoint dot to cowitness with the irons in the lower 1/3 of the tube?  why is that?

As to mounts, initially I was planning on the ARMS #22M68 to mount on the hump.  Now, my choices have been opened up to the PRI and LaRue.  

Is the hump considered the best place to mount the Aimpoint?  Is that preferred over mounting it on the HG or on the receiver rail?  On the LaRue mounts for example; if I mount it in a "low" mount on the 'hump" versus the "regular" (higher) mount on the rail or HG, is the cowitnessing ability the same?

Thanks
Rich