Edit: That being said I've heard a lot of mixed reviews on SigSauer ARs and mostly negative on Bushmaster.
Sigs are fine and Bushmaster is probably the most popular 'reasonably priced' AR supplier in the US. I've owned a couple of Bushies and shot several more and there was absolutely nothing wrong with them.
But they are ARs and a lot of people with zero clue have bought and continue to buy them. They then get their internet keyboard warrior armor on and say "Bushmaster sux, so happy I now have a Noevske'. Yawn.