Have not ridden the D6 but the R6 is such a sweet machine. I have an '03 and the power delivery is smooth as Jenna Jameson's sweet globes of love. Throttle response is crisp like an autumn morning! It's more nimble and agile that a double jointed hooker! It can do everything and more that you ask of it. Plus there are a ton of go fast and look good parts out there for it. For what it's worth and it's my 2 cents, the 6 is some serious shit!
The R6 is the best rated 600 there is ('03's at least). That's why I got mine... I mean, I didn't even consider the Triumph. Yeah, it's practically a brand new bike now, but it's still behind compared to the Jap bikes...
A recent article in my local bike mag rated the D6 as the worst of R6 CBR600 Kwaka636 D6 GSXR600 and Ducati750. They were undecided as the winner as the Jap bikes were so close. The pros took all the bikes out at some annual event ( can't remember the name) and about 75% rated and rode the R6 the best. I'll get the event name when I get home and re-read the mag.
"I drink to make you interesting"
JL is 100% right. Check into used '03 R6's. I got mine for $7100 with 400 miles on it cuz some jackass knocked it over in his driveway while washing it so he decided to trade it on and get a new one. You couldn't even see the damage save a little scuff mark on the upper fairing near the right side mirror. And on the stock pipe to but who cares about that shit.