I've read on the internets that the best way to install a seat is the way that gets in in the tightest. I had a carseat tech tell me in person at an inspection that LATCH was best, no matter what.

I installed DD's new seat (a second seat for DH's car) last night. For some reason I couldn't figure out the damn LATCH install. But the belt fit is awesome; by the time I got it tethered, it doesn't move at all. So a proper belt install is OK, right?

That tech's head is full of rocks. She should be reported to SafeKids for her advice, really.

You were correct...whichever method gets you the best install is the best for that seat and that car. Neither lower anchors nor seatbelt is safer.