It's sometimes difficult to find that "Baby Bear" action that works well enough for every sound. Too light (and shallow), and Acoustic and Electric Piano sounds are less responsive and expressive...too heavy, and most other sounds, like strings, brass, organ, sax, guitar (to name only a few) become tedious to play...especially fast runs and repetitions.

That's why I like the Tyros4's FSX...it's an excellent compromise, and (most importantly for me) manages very well with Piano/E.Piano sounds...it also lets me do without the expense (and complexity) of two keyboards, especially important if I plan to gig a few times a day or several times a week.

The aftertouch lets me add expression without taking my hands off the keys...the T4's SA/SA2 sounds also let me do this.

A keyboard under 50 lbs, in its case, is still quite manageable for me, especially if I really like how the action works for me.

Ian