Dedicated circuit

I read a lot of posts on the subject, but my question is I have 6ga feeding a subpanel . My 220 compressor and other circuits are fed from the subpanel.
Should I run my dedicated circuit off the main or would it be ok to pull from the subpanel?
If I run from main it will be close to 100ft of wire, so would be best to use 6ga.
Or, off the subpanel which would be about 40ft, then I would use 10ga from subpanel to dedicated outlet.
Any opinions?
Thanks