1gb is plenty as long as you aren't streaming music/movies over your cellular data. Plus OP is asking about his single line, not a family "share everything" type plan.
Just like you said, unlimited data is now $80 a month on T-mobile. Not to mention the additional $27/mo someone would pay T-mobile for the 5s Equipment Installment Plan. $107/mo? **** that!
T-mobile
3gb plan = $60/mo
iPhone 5s = $27/mo (24 month EIP)
--------------------
$87/month, no thanks...
Verizon
1gb plan = $60/mo
iPhone 5s = $200 down payment (basically $8/mo over 24 mo)
---------------------
$68/month, sounds good to me!
Not to mention the fact that T-mobile has terrible building penetration and their LTE coverage pales in comparisons to Verizon's.