Actually...both!!
The special Bondo that I use is a very fine grained Bondo that is used for spot puttying.
Glazing putty, from what I remember of it, is just a laquer based goop and is NOT catalysed.
The stuff I use requires a hardener, like Bondo.

And a little goes a long way. The 1/2 full can I have, I've had for like 15 years!