NT3
I can't give a comparison but I do own a pair of NT3's and have been very happy with them, specially considering the price. Unfortunately I haven't used them to track drums so I can't give you a real good idea how they would work for that, I use mine mainly for acoustic/electric guitar and voice for now.
I have heard that they can be a bit harsh sounding in the upper frequency range, such as with cymbals, but I can't verify this. I've seen some postings from people that disagree and have used for this and they were happy with the results, especially when factoring in the price of the mics.
I have done some room ambience micing with them and didn't notice any harshness to the cycmbals but this is very different than using for overheads so your results will vary I'm sure.
From my experience with them I'd say the NT3 would be a GREAT budget condensor for piano, I really like the results I get from using them with my acoustic guitar.
My .02
You should do a search for both the mics, I know the NT3 has been hotly debated and you could get a lot more info on them from reading past posts.