There is a monetary limit to SquareTrades policy. They will only pay for repairs totaling the original cost of the phone. Source:
http://help.squaretrade.com/help/helparticles/How-many-claims-can-I-file
So since Apple charges $549 for "Other" repairs you would only get one full replacement then be on the hook for $98 for your second repair if it required the entire phone to be replaced. With screen replacements Apple charges $279. Lets do some math.
Total Phone Replacement (assuming 2 full phone replacements/repairs)
SquareTrade:
Claim Balance: $1000 (original purchase price) - $549 (1st incident repair fee from Genius Bar) - $549 (2nd incident repair fee from Genius Bar) = -$98
$129 (2 year plan) + $99 (1st incident deductible) + $99 (2nd incident deductible) + $98 (out of pocket difference) = $425
AppleCare+:
$199 (2 year plan) + $99 (1st incident deductible) + $99 (2nd incident deductible) = $397
Difference: AppleCare is cheaper by $28
Screen Replacement (assuming 4 screen repairs are required)
SquareTrade:
Claim Balance: $1000 (original purchase price) - $1116 (4 X Screen replacements repair fee from Genius Bar at $279 ea.) = -$116
$129 (2 year plan) + $396 (4 X incident deductible at $99 ea.) + $116 (out of pocket difference) = $641
AppleCare+: $199 (2 year plan) + $58 (2 X incident deductible at $29 ea.) + $558 (2X Out of pocket screen replacement at $279 ea.) = $815
Difference: SquareTrade is cheaper by $174
So I really guess it comes down to how many times you plan to break you screen as the full phone replacement is almost a wash.