The polymer lowers are also easier to mill i think.
Yes I know, I was just saying that they might be easier to mill without having to invest in $500 worth of tools and jigs.
Yes/no.... having done 3 Polymer 80 lowers, I can say reliably that one should never drill out a polymer kit with hand tools... I've seen it done on youtube, but it is way too easy to have an oops that destroys the blank. I did mine with a 10" bench drill press and I soon bought a cross-slide vise.
BTW, I ruined a polymer lower by having a bit of slop in the trigger pin holes, then using Loctite to hold the heads of the anti-walk pins. Uh, that's a nono... melted and cracked the lower.
I've not had any issues with longevity with those lowers, but then I don't shoot 2000 rds/day.