I have both, drilled the same (pin over fingers, cg in palm) and I try to keep the Optimus at 2000 abralon and the Nano at 4000 abralon. The difference I see is the Optimus has a stronger motor, so once the ball gets started, it is stronger than the Nano. However, the Nano is essentially or is a particle cover, and the cover is stronger than the Optimus Solid cover...meaning the stronger tire has a tendency to check sooner than the other ball with a weaker tire but stronger motor.
In relative terms, I still see the Optimus solid as more ball than the IQ Nano and I see enough difference on tougher conditions to have both in my bags.
I would in NO way say the Optimus Solid is a replacement for the Marvel S as the S is a Nano cover just like the IQ Nano. I have been looking for a Marvel S to go above my Optimus Solid