Well the heft of steel vs. LW polymer... tough question.
I have both and carried heavy pistols 40 years, mainly a Colt Series 70 45ACP. I now carry a Glock 23. Lighter, just as strong and easier to manage. Recoil is a bit more but not bad. I'd say today polymer makes more sense but can you rent both and find out which works out best for you?
The biggest issue with assembling an AR isn't so much getting the parts together right - it's getting the right parts together.
US Army 1966-69, VFW Life Member, Retired Geek