Phone option is good, sure. However, in live use I much prefer onboard control. Wireless connection can be unreliable, or you have to think "where´s the phone?", or you have to grab it "somehow", or sliding in the screen could be a mess, not having precise control of what the valule is, maybe even not seing it because your hand is in the middle of the number and your eyes, etc.
Phone option is better than nothing, but for me, it´s not comparable to just bend down to the unit and touch a knob in a couple seconds when you´re in a rush.
For me, useable onboard UI is a must. Not neccesary a fantastic, cool designed, mega-modern UI. Just a quickly useable one (even the ones from the GT-1 or similar).