Best Cerb to Buy?

[GasBlaster]

I am very tempted to upgrade from Griff500 to Cerb.

With engines - like breasts - bigger is often better, so is the 4.5 a better bet than the SP6 or 4.2? And is a Lightweight much better than a regular 4.5?

I would be interested to hear views on anyone who has made the transition.

What are servicing costs like vis a vis the Griff?

All opinions welcome!

Thanks