First off, I have an ARMS #40 and I love it. I purchased it based on the recommendations of countless members and because 1) I didn't want to look at a sight I wasn't using and 2) I wanted the ability to upgrade to more equipment. I'm now using an Aimpoint and a SIR with it, so I'm extremely happy with my BUIS choice. In retrospect, if had wanted to use a FF RAS or RAS II, I'd be wishing I had the LMT right now. When I shoot with my #40 up, I NEVER notice it until I want to. I've become fond of having it up with the small aperture, as I seem to shoot better at a distance using the irons and the Aimpoint simultaneously (perhaps I'm just weird). Basically, it depends on what your end goal is. If fixed irons aren't going to get in the way, go with fixed. (I've never actually shot with an EOTech, but from looking at it I'd prefer the #40 with it because the lower height.) If you want the option to get magnified optics or a SIR, get the #40.