E80... fewer sounds, but better, more recent ones (G70 has a lot of older G1000 sounds for backwards compatibility).
E80... 3 MFX insert effects, on Song, Style or Keyboard Parts. G70.. One MFX on Keyboard only (although there's an easy workaround to get one more, on song/style or keyboard part).
E80... Two Master Effect (3-band comp and EQ) on Style/Song and Keyboard Parts. G70 one Master Effects on main output.
E80... text to style AND song display (with bitmap graphics display, too), G70 text to song only (sigh!).
G70... Main AND 2 direct outputs AND Vocalizer outputs, E80 Main outputs ONLY.
E80... 61 keys G70.. 76
E80 has speakers (and weighs more!)
E80.... 2 SRX slots, G70... one.
Some minor OS differences, nothing major.
Hope this helps....
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An arranger is just a tool. What matters is what you build with it..!