I haven't thrown either the Nano Pearl or Marvel Pearl. I have the GS and 2 Marvels so I'm familiar with the ball motions from those cores. My GS was a monster on THS and from what I've seen of the Nano Pearl reminded me of a stronger GS but I'm sure the Marvel Pearl is stronger than GS as well.
Just my 2 cents, if that. I certainly would trust other's who have actually thrown both balls though.