he is full of horse dung. he is trying to steer you into buying his shit.
AERO is made in washington state. PSA uses governemnt contractor parts from what i have seen there all CMT made like stag and rr--
i haven't handled any of their lowers but i figure there made by LAR which supplies most of the lowers on the market.
there is nothing really wrong with a del-ton, i have several uppers made with del-ton parts/barrels.
i am not crazy about del-tons bolt carrier groups but they are ok but certainly nothing special.
del-ton is OK for the price but their certainly not the bang-for buck they once were.
if i was buying a del-ton i would buy it from JSE rather than directly from del-ton.
one more little thing--- AR-15 parts arn't importable from china, they haven't been importable from china in a long long time. you pal is way out to lunch on that one.
del-ton is sort of the "low dollar brand" sort of like DPMS or DSA.
i use lots of their parts there certainly good enough. personally i rarely use their bolt carrier groups though they are good enough a BC-usa. LMT or mill surp carriers don't cost much more so that is what i use mostly.
the most expensive and critical parts on the ar-15/m16 series are the barrel and the bolt carrier group. my advice is to get the best quality you can afford for them.
i haven't heard a peep bad about PSA's other than your post. there bolt carriers that i have seen are excellent. they look identical to stag/CMT & their barrels may well be made by del-ton which is a good brand and they use 4150cv steel in their 14.5" and 16" barrels these days so their not far behind bushmaster or colt even. even if they ran that mall-ninja four letter word (DPMS) i have several of their barrels and they all shoot very well.
another place you should look is over at DSA-- they have good prices and they are related to LMT , they sell a lot on nitrite treated barrels which many think are the cats ass.
AR15 Lowers & Uppers-D S Arms
what to buy in your case is what you want. the world is full of m4 type arms and parts , there about as cheap as there going to get , most of the stuff out there is good , hell some even like hess AK-parts and i know they toss in a dew duds--LOL!