andre_
is a big difference between the two. IMO, the E50 styles and sounds are very advanced and modern, while psr1500 is after all 2-3 years old. now, of course, that depends also if you like batter the yamaha styles or roland's. but i can tell you, after playing both, i would pick E50 at any time!
scott_
to change/choose a sound on E60 is a two step thing. first, press the section (left, right1, right2) button and then press the sound family button. the last sound you used from that family is selected, and at the same time the screen displays 10 sounds (= one page). it's very easy to pick a sound or another page, because you just press what you see on the screen - is very handy!
the styles are about the same: press a family button, and the displays shows 10 styles to pick from or the other pages to go to.
for me, i think E50 OS is about as simple to use as yamaha's psr. a little bit more complicated with the user programs / registry, but not a big deal.
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Yamaha S770, Studio One 3, EMU 0404USB, ESI, ATH, Dell. And others.