I already have both games in disk form and have purchased Freespace 2 from GoG already, but I think it would be nice if they found their way on Steam too.
If I had to buy again given the choice between GoG and Steam and assuming the Steam version doesn't have any compatibility problems, I'm not sure which one I would pick.
I mean, yes Steam is DRM.
On the other hand it has some nice benefits (easy replacement of bad files, in-game chat, ect). Also, it's done a lot to keep some of my favorite indie developers going (Introversion and Frictional among them). There's also the fact that I probably wouldn't have found some of my current favorite games without it.
It's like the evil umbilical cord that's giving me so much candy that at this point I usually don't care that it's an evil umbilical cord anymore.

As always your milage may vary.