I have a Vortex SPARC red dot currently on my AR, but I've been thinking about upgrading to a used Aimpoint Comp M2 on Craigslist for around $400. Is it worth it? I'm not kicking down doors in Kandahar, so bomb-blast-surviving durability (besides waterproofing, which the Vortex is already very good with) isn't an issue. Thanks in advance for your advice!