I have flown both quite a bit.
Personally I marginally prefer the G1000 to the Avidyne - if I were buying a Cirrus if I could I would want the new Perspective model with the Garmin and the Garmin autopilot.
The Diamond better fits the mould of a training aircraft. The performance is lack lustre compared with the Cirrus. However, it is a great deal easier to fly (depending on your experience level). I would expect the average PPL with 100 hours under his belt to be happy with the Diamond (G1000 aside) in a few hours at most, whereas the Cirrus might take any where up to 30 hours.
I can give you a lot more information but how relevant this would be without knowing your background and the purpose to which you would put the aircraft is questionable.
If I had to sum up in a few lines I would say they are two very different aircraft. If you want an aircraft with performance, serious touring ability, good load carrying and reasonable all weather IFR capability then the Cirrus would much more closely fit the bill. If you want an aircraft that is simple to operate, reasonably fast, will cope with reasonably benign IFR work and will be less costly to operate then I suspect the Diamond would better suite the bill.
I can only reiterate that they are a great deal more different than you might think so you would be wise to match the aircraft to your needs.