I'm pretty sure that the iPhone's processor is faster than the Storm's processor. I've used my friend's Storm and it's very sluggish compared to the 3GS. I don't know how fast the iPhone can get, the 3GS is pretty damn fast compared to the original iPhone and many other smartphones on the market. I can't say I've wanted it to be any faster since I got it :S
If you jailbreak your phone, nothing will happen to your app store apps. But make sure you right click your iPhone in iTunes and "Transfer Purchases" so that if something goes wrong you have your apps and their data on your computer.