there really isn't much difference between the "graded hammer" and "Superb Graded Hammer" (supposedly it's different, but I don't see any difference.).. I'm my opinion, its the same thing with the word 'superb' in the front,, There is, however a GH3, which yamaha claims to be most realistic action on a digital piano... but its only found on the "Clavinova Digital Pianos" like the CLP which you don't want cause they are not portable...
I like the P90, very portable,, sleek and easy to use.. but no speaker. If you want speakers,, then I'd go with the P70 ---
p.s. that P250 is huge