Although this has been discussed in earlier threads, I want to emphasize that Sprint has NO deductible on repairs. The deductible is ONLY for lost or stolen phones.
Thus, I see no particular plus from Best Buy. As has been noted in previous threads, Best Buy will often take your phone for many weeks in order to REPAIR your phone. You are not guaranteed a new phone until they can't repair the phone that is broken. Plus, for your $3, you get no theft or loss insurance. Best Buy is not the way to go.