Having just bought and watched the BMI DVD on the FD2 I have to say that its a SERIOUSY impressive car 8)
Gears 1,2 and 3 have been shortened, and 4,5 and 6 lengthened compared to the DC5. Engine's been tuned to give much more mid range torque as well as a few extra bhp. In a straight line its quite clearly faster than a DC5 as a result.
On track though its just frighteningly fast. Fastest production 2.0 n/a car ever, and faster than everything this side of an NSX Type-S. It can only be described as a race car with number plates, and from the opinions of the BMI staff it truly is a Type-R.
What I would say however is the interior of the DC5 is of a higher quality (recaro seats, steering wheel etc). IMO the DC5 is the better looking car, but that's not necessarily fair on the FD2 since the DC5 looks better than most cars under about £40k!
Lastly the ride quality on the FD2 seems seriously compromised, particularly for passengers. BMI actually made quite a big deal about this. Clearly setup for the track, I think the FD2 would really struggle on the roads in my area in particular.
So there it is. The FD2 is a cracking car, and will no doubt go down in history as one of the best cars ever.