At this point T4 is a Great sounding HOME players unit & the new Pa3x is much more from it's aluminum body, black look, sliders, Tc VH, editing, touch screen, chord sequencer, dual Mp3, & soooo many more features geared for a "live gigging musician"....it's a difficult choice that needs to be weighed by the individual needs of the player.
they are all great instruments. They aren't toys. They will sound as pro as you want depending on how pro is the player. The Tyros is a pro instrument as it is the Korg.