I guess it's like anything, depends on how you're going to use it. Something like a S&B Short Dot would work pretty good as an all around optic especially for a civilian or LE. The ELCAN isn't a terrible option by any means. I personally like to have a 1X red dot so I'd probably use an ELCAN over an ACOG. The only ACOGS I've tried had pretty unforgiving eye relief. A traditional scope of some sort, preferably something lightweight, coupled with a Horus reticle might be pretty sweet too if you're mostly wanting to shoot at medium to longer ranges. I'm not any kind of authority on every different optic available for private purchase but if I had a SCAR Heavy in my safe right now I'd either be saving up for one of the new 1-8X optics or I'd just get a 1-4X ELCAN for it. I'm sure there are people out there getting good use out of their Mk-17s with Aimpoints mounted to them or even just irons, it just depends on the application.

Has anyone tried using an offset RDS on either version of the SCAR? I don't see any reason why it wouldn't work but I haven't actually tried it myself.