I am a fan of the Motorola DROID 3. I currently have a DROID X2 and I love it! The only difference between the X2 and 3 is the DROID 3 has a full QWERTY slide out keyboard, and the 3 has a front facing camera. On with the features.
Apple's iPhone 4
Largest app store
HD screen
Can pay for apps/music with gift cards, no credit card required
Back camera, 5.0 megapixels (more vibrant colors than DROID 3)
Front facing camera 0.3 megapixels, great for video chat
Very nice layout total
Motorola DROID 3
Vast app store, with more free apps
HD screen
Full slide out QWERTY keyboard, very easy to use and get used to
Back camera 8.0 megapixels, HD 1080p video
Front facing camera, 0.3 megapixels also good for video chat
Dual core processor (overall faster and smoother performance)
Widgets available, display information without having to open any apps
Also a VERY nice layout
I have had experience with both devices but I can vouch for the DROID especially as a great device. Both are excellent choices.