The bigger differences between the phones are storage capacity, application access, video capture capability, weight
The iPhone comes with 32Gb of internal storage space while the Droid only has 7GB, but the Droid also has a MicroSD card slot which allows for up to (according to current standards) 32 more gigabytes of storage. As far as applications are concerned, although the iPhone has access to the bigger Apple Store, the Android Market is less restricted and thus offers more variety and less censorship.