The comparison between the iPhone 4S, Samsung Galaxy S II, Motorola Droid Bionic and HTC Titan has been done on all performance levels. So, regarding processor power, Galaxy S II from Samsung beats the iPhone, as it has a 1,2 GHZ dual core processor compared to the iPhone 4S which comes with a 1 GHZ A5 dual core processor.
Regarding storage space, all three rival smartphones have 16 GB, and they also offer the possibility of using a memory card.
Regarding display size, the iPhone is small compared to the competition. Galaxy S II and Droid Bionic come with a 4,3 display while the HTC Titan comes with a 4,7 inch display.
It would be interesting to see how all these smartphones will compete with each other on the market.