The main differences are:
- 16Mb Ram on 615 vs 8Mb on 770
- 8Mb Flash on 615 vs 4Mb on 770
- Multichanel soundchip with built-in speaker on 615 vs crappy singlevoice buzzer on 770
- no MP3/ audio outlet on 615 vs really cool MP3 replay on 770
- unconfortable buttons on the 615 vs not so bad ones on the 770
- the screen appears slightly more contrasted on the 615. But I guess all recently crafted screens are this way, no matter the device.
- the 615 bow is definitively thiner than the 770 but somehow slightly wider.
This information comes from a comparison (one in each hand) I could perform between my 7x0 and a borrowed 615. If I had to choose now for a new device, well, I only know it would be a tough decision to make. I may go for the 770 again coz the crappy buttons (cannot play with those) and lack of MP3 on the 615.
WM