Depends on what you want it for.
For most of my work I use Tamiya. I don't have issues with Testors because I haven't used it in a long time. One other gent swears by Squadron.
Bondo 1-part is good, I used it to level a top on a resin car but it was a thin coat.
For heavy filling and mods I use 2 part bondo. Bonds well, dries hard, and doesn't shrink.