Best way to decompile maps?

What is the best way to decompile .bsp files or convert them to another format? What would be the best programs to use? I’ve had a look around and I’ve found VMEX and Object Viewer, but neither of them were very good.

Vmex works nearly perfectly fine, aside from a few hiccups once in a while. What format are you trying to convert them to? You can try BSPsource if you want the vmf, then use wall worm to convert that to any format 3ds max supports.