They're both great cameras. I was trying to decide between D5100 & D7000 to replace my D100, so I went to a store and held both. The D5100 just feels too small in my hands. Some people love that it's small. I just feel more comfortable with a larger one. Just remember, no matter how good a camera is, you won't love it unless you like the way it feels in your hand. Also, if you like direct access to functions, the D5100 may not be for you. You have to use the back screen to do alot. Go to snapsort.com to compare specs, then go to a camera store and hold them in your hand. You may also want to consider a used D300 or D7000. Personally, I chose to wait until I saved up more money to get a D7000. Hopefully it will last me almost 10 years like my trusty D100 did.