From what I've gathered, of the two models you've suggested, I will mention a few of the apparent differences (from looking at the spec sheets):
The Kurzweil SP76 - Has MIDI capabilities, has 32 polyphony, and is Semi-weighted.
The Roland EP-760 - Does not have MIDI capabilities, is 64 polyphony, and has weighted keys.
These three factors should be addressed (as far as basic specs go). MIDI capabilities should speak for itself, at least as far as your requirement/want, is concerned. Max polyphony depends on your style of playing (32 may not be enough, expecially if you intend to play classical). Weighted keys are always a factor that depend on your playing style (my personal belief is that weighted keys are the way to go, expecially if your goal is to learn the piano).
Some other factors to be considered: The weight of the keys - are the keys too heavy, too soft, sluggish, ect. (play testing is the only way to determine your preference, although a general idea might help in getting recommendations)? The sound - are there noticible differences between notes (ie. does one note at any given level sound like a stienway grand and the note 'next door' sound like a yamaha upright)? Are there onboard speakers, or will I need some sort of external sound system? How many different sounds/voices do I want?
It all depends on your needs, wants, requirements, budget, and taste.