EOTech vs Aimpoint for a fighting carbine?

Different tools. The EOTech holographic reticle (a big ring with a center dot) is extremely fast and pairs naturally with a magnifier — great for close-to-medium work. The tradeoff is battery life measured in hundreds of hours, not years, so you manage power. An Aimpoint is simpler, lighter, and you leave it on for years. If you want the fastest reticle and a magnifier setup, EOTech. If you want set-and-forget reliability, Aimpoint.