Imbel vs G1 vs L1A1 vs anything else

I've seen parts kits for each in Tapco and FAC, and receivers in FAC by Imbel and various US manufacturers.

I hear that Imbel is better, and I would guess that the fit and function would be better between an Imbel receiver and parts kit than between a G1 parts kit and US made receiver. The US compliance parts (stock set and fire control parts) all come together anyway, so a US made receiver isn't necessary.

Or should I consider a different set of parts and receiver?

And how would this compare to a pre-assembled L1A1 from Centerfire (presumably Century... anyone else make them for under $500?)