Both are great lights - I run an X300 on pretty much every RDS equipped carbine I own (and pistol), and an M300 or equivalent on everything with a variable zoom optic. This has as much to do with the iron sights as anything else (I love the DD Fixed Front with an X300 directly in front - it also does a lot to mitigate the ALD issue as well).
If you're running an offset mount anyway, i HIGHLY recommend looking at running a VTAC L4 in an offset mount - it's a scout head and tailcap in an E body, for a great price - run that in a good offset mount (GearSector, 03DG, IWC, etc.).
the x300-Ultra and revised Scout lights both have absolutely bonkers lumen outputs, which is great, and that's not worth picking between them. I'd simplify the decision to how much the ambidextrous actuation makes sense (the 12:00 directly in front of a fixed iron sight setup is my absolute preference for the X300), or if you need the offset actuation to be really happy with it (if so, the M300 and VTAC l4 3V are both awesome). I have piles of each, and am VERY happy with both for the desired applications.
Last edited by TehLlama; 06-04-13 at 21:50.
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