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?
If I were to get an answer from @jea48 ,
I would take it as gospel.
Just do a search of his responses over the years and you can see why he is trusted-almost as much as the late Almarg.
Thanks for the kind words.

I concur with jea48.
+1 for Jim also..

Unfortunately, the ac compressor is going to infect the whole house, it won't be confined to the subpanel. Running a 100 foot branch circuit makes it a magnet for EMI generated throughout the house, so I would use 3-wire romex. The wire is pre-twisted and helps with rejecting common mode noise, which could be a problem at that distance.