Problem is, (last I checked) Best Buys insurance is not nearly as comprehensive as Sprint's. For example, Best Buy does not cover lost or stolen phones. Sprint will cover about anything and everything that could happen to the device.
If you skim through the EVO 4G forums, you'll see a lot of pissed off people that had to deal with BB's insurance... long wait times to get a replacement at Best Buy. With Sprint you will get a new/refurbished phone the next day, overnight right to your front door.
I think you fudged the deductible, too. Last I checked it was 50 for non-smartphones and 100 for smartphone.