No comparison. A real arcade trackball is vastly superior.
Depends on the TB. Kensington makes some very high quality PC trackballs, that compares very well against the same size (2 1/4") arcade TBs.
If someone wants a 2 1/4" high ball TB, with very fast spin and a light weight ball, a Kensington Expert is a very valid option.
IMO, I find the Expert better for me over a happs 3" high ball. Of course, I'll take any other arcade 3" over my expert. (The high ball pops off the rollers too much from my hand control, which gives the expert and happs high ball minus in my books.) Of course, this is much like people's favorite joystick (different opinions).
Other than the Expert, though, yes, arcade TBs are better than PC TB hands down.