u/swirldad_dds - originally from r/GenZhou
Whichever org is the most active in your community honestly and does actual Praxis. Socialist Alternative does some good work in some places as well, I think they might be Trots tho....
Edit: I also remember seeing a thread on here a while back that said CPUSA is the only party in the US that has active relations to the CPC, so that's a point in their favor