I'm switching my phone service to AT&T sometime soon and I was wondering about the two iPhones. When we asked about the 4G the woman told us they were out of stock because of the holidays. However, she had in the 3GS for $100 each with an Otter case free. Is this a better deal then the $199 4G? What I'm mainly asking is are the improvements on the 4G worth the extra hundred?