A lower is a lower is a lower. As long as all the holes are correctly sized and in the right location everything else is brand loyalty.
Tactical Innovations T-15 lowers come with a set screw to eliminate play between the upper and lowers and I know there are other manufacturers who do the same. Does the job of the accuwedge, and if you feel like spending the extra $50 because it makes you feel better it's an option.
But otherwise, yeah, a mega isn't any different from a del-ton isn't any different from a spikes. Although my RRA has a less glossy finish in comparison to the Del-ton lower...