With that as a given it is no surprise that the first campaign I attempted due to OSR inspiration used Basic Fantasy Roleplaying. Even now with Advanced Edition Characters I think BFRPG does a better job of capturing the “intermediate D&D” I played in the late 70s and early 80s.
Last year when I tried to restart Swords of the Red Sun I again went back to BFRPG as . See the notes on the Clockwork Skeletons post for evidence.
In the vast array of retro-clones why would you choose BFRPG?
First, it is the only one to do the ID&D feel: Basic combat with Advanced Race/Class split right out of the box. Second, it is non-commercial which means its community has a slightly different feel. Finally, there is the community around it. Because they are the “redheaded stepchild” (or the little redheaded girl) of the OSR the feel is a little more offbeat.