I dont actually have one myself but played all you mentioned at the SamAsh near me a while back.
I think the Axon is the best; but the Yamaha g50 is about the same. The Yamaha used 12 bit converters to the Axon 16 bit but its hard to notice.
Yamaha had some real nice auto setups with their module; the TX81Z still sounds great to me.
The Roland was actually okay too. But the Axon is best.