moleDave_dt880s are good. I've had mine for a couple years now. They're a lot better sound wise than the dt770s.
I tried them for 2 hours or so at a local store, and I found them to have too much sibilance, almost hurt. Also saying "sound wise" doesn't really say much, you need to be more specific, what was better?
Found a guy on a forum saying "I really enjoy my dt770. On the other hand I really hated dt880" (http://www.head-fi.org/t/723025/philips-fidelio-x2/3930#post_11378390), so it's definitely not as simple as you made it seem.
They have a better frequency response + soundstage. If they're too sibilant just get the 600ohms; they are less sibilant than the 250 and 32ohm. If you're looking for something that's more neutral, the dt880 is a better headphone. If neutral isn't what you want/the sibilance bothers you, get the 600ohm or just use a diff amp idk. I don't have that issue with my current amp/dac.
If you're seriously considering them/on the fence between them, read this, specifically post 2: http://www.head-fi.org/t/258751/dt770-vs-dt880