I have played EM55 and EM25. They are different.

EM25 has usual voices as others EM (EM50, E-36, E-38...); it has less Mb for sounds (1 Mb), but it sounds nice.

EM55 sounds fonts come from VA series. So, EM55 has a lot of voices, I think the same as VA3, and with similar Mb (8 Mb). VA5 and VA7 have similar voices, but they have a lot more MB for these voices, and so they sound very very better, better (you may compare piano sound, for ex.)

But EM25 is pretty (for its price). Its piano sound is, for my ears, better than EM55 or VA3.

As you say, on these kbs it is no possible to edit styles, but on EM55 you may mute (not edit, only mute) each part of arrangement, and you have also something similar to pads you may see on Yamaha or Technics keyboards.

But for the price of EM55 (similar to PSR1000), I think Yamaha offers more. Specially I don't love EM55 piano sound, and its impossibility to edit styles.

Cheers

Artaher