In my area, we see a bit of everything in terms of shingles. I’m not a roofer, but I can tell you what kind of companies in my area use which.
The bottom of the barrel roofers use only IKO and Tamko. The middle of the row guys use OC and GAF. The only guys I would trust to do my roof and do a dang good job use CertainTeed with a few opting for Malarkey or Atlas.
When hail storms came through, a lot of people had GAF shingles put back on or OC from the middle of the row guys who weren’t as booked out. I can tell for certain now which houses had GAF shingles put on compared to OC or CertainTeed. The roofs just look off, almost like the shingles are thin and don’t lay quite perfectly. Every CertainTeed roof I’ve seen looks great.
All my contractor friends and people I know in construction opt for a CertainTeed roof.