For BB it seems better to just break your phone beyond repair so they don't have to send it to get repaired. But ya even if you get a gift card you still pay tax. So that means...
$55 avg tax + extra $3/month vs sprint for 1 yr is $36
You're not really saving that much plus the headache of waiting in line and lost, stolen, and full water damage not being covered.
So Sprint FTW