Well, I mightn't go quite that far. The native browser on the 808 is fast. The N9's makes a better use of the available screen. The difference in screen resolution is noticeable here. That said, the larger type on the 808 screen is a little easier on my (older) eyes.
Tight integration of multiple accounts on the N9 is hard to give up. Mail for Exchange, however, on the 808 synching Gmail, Contacts and Calendar with Google is painless. On the N9 I have that spread over three separate implementations - Gmail within mail, MfE for contacts and CalDAV for calendar. That last, however, does allow me to sync three different calendars.
MeeScan on the N9 works better than a couple of QR code readers I found for the 808.
The Twitter mobile page seems to work better on the 808 than the N9 - it's faster, which may be why.
I got away from the multiple home screens of my N900 when I went to the N9. I'm finding it annoying to have to dedicate 4 home screens to get to what the Notifications view on the N9 delivers. And delivers in a much cleaner and smoother (particularly now under PR1.3) way.
The fact that the app screen on the 808 shows 12 app as against 24 on the N9 means I have to scroll a lot more to get what I want. It's one of the clearest views of the importance of screen resolution.
I love ProfileMatic on the N9. I haven't tried Nokia Situations on the 808 as yet.
Nokia Sleeping Screen I remember from my E7 and it works fine as far as I can tell on Belle FP1.
I'd ripped my music to lossless FLAC for the N9. The 808 couldn't play them so I had to convert. It's OK. I'm not expecting music system quality out of my phone - I have full range electrostatic speakers at home for that.
Symbian isn't the dreck so many tech blogs would have anyone believe it to be. It works well on the 808 H/W. But, I got used to a much smoother and integrated experience with the N9 (and excellent integration with the N900.) I still miss the N900 tag cloud when sharing (particularly when I used PixelPipe) - even on the N9.