His experience on the M1 will not be of great help to him as a Pa-Series Arranger operates only slightly like a KORG M1 in SOUND mode.

Why is he even considering a Arranger in the first place if he's playing a Workstation?

Tell him to go try a KRONOS. He will feel far more at home there than on a Yamaha or KORG Arranger and for sounds, it would destroy them both.

Regards
James