First, there is no comparison of the G70 to the low mid line S750 and Pa600..The G70 is a pro model, built to be played on the road...

It does split in 3 zones and will layer 6 tones..

As a midi controller ..it is like other arrangers..you can send arranger data, and realtime parts, also midi file play, but limited with midi cc control other than after touch, modulation, pitch wheel, and cc7 (volume)..

Soundwise, it is still the best..sure every company has it's best sound that stands out...Piano, organ, choirs, synths are all better on the G70..also drums are better..
When you add SRX board ..all sounds are better..including guitars, Brass, reed, strings etc..

You cannot add samples other than the excellent SRX board, with immediate selection to play..
BK series styles will play on the G70, and it has the best editing capabilities of any make..

The external card is for styles , SMF's and system data including user programs..
Nothing breaks on a G70...
Hands down..the best buy..