Protostar is a bit lighter, I think 3 grams, and does play very floaty.
Northstar is and feels a tad heavier on hand, but both yoyo’s can do same amount of tricks.
Both have little plastic vibe, usually doesn’t bother me with a good throw.
I like the Northstar better IMO because when there’s vibe, I don’t feel that the yoyo is “hollowed” out.
What I mean is that when the Protostar hits the end of the string, I feel this “hollow” feel and sound. And add vibe to that, “hollow” vibe. I’m fine with that, but not my favor.
I have a Protostar and really like my Protostar, but I generally like a more solid feeling throw so I’m thinking of getting a Northstar or Rockstar. Sometimes it just feels like my Protostar doesn’t have as much momentum behind it as I would like. Otherwise my Protostar is super unresponsive, and has a tiny vibe with the yoyo slightly overtightened (there is a slight pulsating vibe with the arrows matching).