I like both. The spin time is a bit better on the protostar because of the center trac but I would get the dv888. Plus the dv has better speed. They are very alike but the dv can grind. Stabity I think the dv is better. The north star is like the proto star but more stability.
The CT bearing doesn’t help the Protostar and Northstar much if any. CT bearings do not change spin time, though in rare cases, it helps the string away from the sides of the yoyo in which has never been helpful.
If you have a good throw, a YYJ Kickside spins just as long as a OD 54.
Dv888 is more stable, as because the Protostar is quite light and “hollowed out”. Dv888 is made of metal, also having a heavier feel, it does not seem to go out of balance.
Smoothness, both. Really depends on the bearing. Fully rusted bearing, no good. Good condition flat bearing, good enough. OD 10 ball, quite smooth.
The Protostar plays faster than the Dv888, because of it’s weight, material, and all other matters that affect it as I’m not an expert at physics, but Dv888 also does play a bit heavier. Not too heavy.