Okay, obviously these are totally different boxes (one's SSL style VCA, the other is FET based), but both are in my price range for a stereo compressor. Mostly planning on using them for mix bus use, generally rock and metal.

Anyway, thoughts on these? If you've compared them, which did you stick with and why?

Why not post some audio and then the hardware owners can process it using your usual ballpark mix bus compression settings. perhaps using a similar plug in first to find your settngs. I know the variables will be enormous but it should give you an impression of the sonic footprint of the units on your material.

Warm gear is decently above Art gear when priced the same.

No experience with the Art,
but at that price I would be looking at Chameleon Labs Stereo Compressors over Art products.

The Warm is a nice comp. Only tried one briefly, no major complaints at the time.
Alternatively, we had two Alctron mono comps linked together which ended up sounding "more suitable".
These are (essentially) Chameleon Labs or Golden Age style low end "clones".
I lean toward defending affordable gear,
so if the Warm is cheap enough (used/affordable),
it's a decent comp (I would never pay full price for).
Same goes for Art, GA, CL, Alc, etc...