As a Pro Tools producer, do you use certain compressors and other out board effects boxes while traking but resort to plug in's for mixing? Or is it plug in's all the way.

Secondly, for outboard compressors, do you find that certain ones (the newer ones) are more suited to the Pro Tools environment while the old school ones were more suited for tape?

Yes.
Not really, vintage compressors get used when recording to digital (DAW/PT/whatever) all the time, as well as newer ones (these days usually emulating vintage units anyway).

Hope this helps.

I like to use every colour available, new and old, hardware and plug-in.