Because I have one of those on a lightweight carbine, and in fact I really do like it. Now I'm building another lightweight that, if I didn't already have the H-1, I'd think it the perfect red dot for this new carbine.

But man, I just have a hard time with the idea of owning two of the same rather expensive sights and, also, I'd really like the new gun to have its own dedicated sight. So what comes close to filling the same niche as the H-1? One option I've considered is the Burris Fast Fire/LaRue Iron Dot combo, but I haven't seen much feedback on it for either function or sturdiness. Any feedback for that? Anything else?

I sold my ML2 and M2 couple of years ago.  When I got the itch to get another Aimpoint, I looked at another M2, M3, M4 and T1.  I got the M2 with a LaRue mount, the battery life and 2MOA of the M3 aren't enough for me to spend extra for it, and I don't like the M4's mount.  The T1 cost more than the M2.  The M2 was perfect for my need for use with NOD.

Later I got a T1 anyway after seeing militarymoron's T1 at the range, but only because I got a great deal from Kiser Munitions.  It's a cool little sight.

If you want variety, then get the less expensive ML2, ML3