I will get to the point and then elaborate. I've had a VECP V.2 and an XM-18 3.5" gen 3. Now I only have the VECP.
Both knives have great fit and finish and ergonomics. Honestly, my XM had a better lock up than my VECP. However, I could not get past the PATHETIC detent on my XM. If I have a flipper I want it to reasonably easy to deploy quickly without a wrist flick. Sorry, but that's just me.
With that being said I'm not sure I'm in love with the blade steel/heat treat on the VECP. I pried a few staple gun staples and rolled the edge of my VECP all to HELL! I'm not sure if that was something that will be worked out now that I've sharpened the edge and exposed newer metal or not. All I know is it DOES make me baby my VECP a bit. I'm sorry I don't believe in safe queens. I use knives!
I'd love to try a gen 4 XM, but I don't think the XM's are worth it, to me, for the secondary price. If I was LEO/Military I think the price is MORE than fair. Since I'll never get that discount, I'll stick with my VECP.