Re: the question about my band (when there are 4 iPads in use) ... well, it's actually a 5pc (and occasionally 6pc) group. Drums, Bass, Electric guitar, Acoustic guitar+vocals, and me on keyboards. (6th member, when present, is another singer). In that scenario, since we have drums, bass, guitars - I use my Tyros5 for sounds (no arranger features). I do use a lot of its sounds - of course pianos, E-pianos, strings, and sometimes horns/flutes/saxes, and B3-like organ, and synth sounds.

For my solo, duo and trio gigs, I use full arranger features. (and one, two or 3 iPads are in use). My gigs are probably about ~40% solo, 30% duo+trio, and 30% "full band" (5pc).

-Jim