Sean, you're basically right about the sharpness.
Noise reduction processing (in or out of camera) reduces detail. It's a trade off, cleaner image, sharper detail. The camera processor uses software algorithms to do the business and it looks like Canikon, with the benefit of experience seem to have a better s/w algorithm than Sony at this time.We all hope it changes.
In fact both the 1600 and 3200 shots have reduced detail but I agree, the 3200 looks better because of the reduction in noise. Actually, I think both pics are an improvement, it's just more obvious at ISO 3200.
I could have played around a little more by applying an unsharp mask, but I chose not to as I think the point had been made.
At this point I should make it clear that I only installed Noise Ninja today and It's likely that an expert will get a better result. It's may also be possible to get a better result by turning off "High Iso Noise Reduction" (available with v4 firmware) combined with proper use of Noise Ninja; beyond my small skills at this point in time.
On a broader note I have to say that 90% of my stuff is done below ISO800 where the Sony is, in any case, the equal of the competition. I'm now pretty happy that the combination of anti shake, "push processing" and Noise Ninja will deliver the goods should I feel the need to go to higher ISO's.