I just read that yoyo factory standerd bearings fit yoyo jam yoyos and probably vice versa… Is one better than the other? Or are they the same?
They’re just different. Some people hate YYJ bearings, but some (Like me) love them, as well as YYF SPECs. I would suggest trying both if you can. Both are the same size (if you get the size C ones).
Yeah, YYF Large bearing and the YYJ Large bearing are the same size.
YYF Spec bearing in my opinion is much smoother than the YYJ bearing. Most of my YYJ bearings rust and don’t spin 
Yeah I kinda noticed a little rust only after a few days… I thought it was natural… But I havnt noticed it affecting my play…