This is the classic Mac vs PC argument. Nothing more, nothing less. Macs are less "customizable" and many want to "mess with their PC". If that is your liking, go with any one of the many flavors of Android. App market is not as mature. Performance across phones for various makers/flavors of Android and carriers differ.
Summary
iPhone- Apple is consistent in hardware/software/performance - known quantity
- All works as designed
- Frequent updates
- Unmatched app choices
- Design/feature leader
- Superior voice recognition
- Slightly smaller form factor (plus or minus depending on user)
- higher initial cost
Android- More versions, different form factors
- More phone choices
- Less apps
- More frequent updates
- Less homogeneity in performance/features
- Lower cost
If you like messing with your phone or upgrading often or if you need a different size or keyboard, Android. If you want something that just works, has superior customer service and app choices and value, Apple iPhone.