Right now, I would think that the "best" .32 Long ammo is whatever .32 Long ammo I could find for sale!
I have shot Federal and Winchester, probably the Federal wadcutter the most, and maybe one box of R-P, but really found all of it shot well. I have shot a small bit of S&B in other chamberings and liked it okay.
Save your empties. Handloading this round is the way to go.
Not much help, I know.