So Square D QO is the best, AND the cheapest?
I patronize my locally-owned H/W stores over BigBox, Inc. whenever humanly possible, but let's face it, Evil Orange's "open 'til 10PM" and Sunday hours really save the day at times.
Anyway, was in Duh Depot recently, and noticed that Sq-D QO single pole "plain" (non-GFCI, non-AFCI) breakers are only $4.98 a piece. Their load panels are similarly cheap, like a 100A 6-slot indoor unit for $22 and change. Buss bars seem to be ALUMINUM?... or is it tinned copper?
Then there's some other NON-Square-D stuff that almost has to be a loss-leader, e.g. 6' long HVAC 30A appliance whip for only $10.04!! That's three different color pieces of approx. 7' of AWG10 stranded copper, 6' of NM-LT conduit, an LT-ell connector, and an LT-straight connector, pre-assembled and ready to roll! I wonder if our pro-sparkies can even get those "raw" components wholesale at that price, let alone the labor saved...?