My search revealed the following results, be sure to let me know what you think!
General Information:
Page Plus Cellular (Verizon Network): $0.08 per text, $1.20/MB for data, minutes never expire, $0.50/month upkeep fee
PureTalk (AT&T Network): $0.05 per text, no data available, minutes never expire
Boost Mobile (Sprint Network): $0.10 per text, $0.35/day unlimited data, minutes never expire
T-Mobile: $0.10 to send, $0.05 to receive, no pre-paid data available, minutes never expire
The Bare Minimum:
Page Plus Cellular: Slightly more than $2.50/month for ~20 minutes
PureTalk: $10/month, 101 minutes
Boost Mobile: $3.34/month, 33 minutes
T-mobile (first year): $8.34/month, 83 minutes
T-mobile (following years): $0.84/month, 8 minutes
T-mobile (avg. after 2 years): $4.59/month, 58 minutes
$10/month Comparison:
Page Plus Cellular: $10/month, 95 minutes
PureTalk: $10/month, 101 minutes
Boost Mobile: $10/month, 100 minutes
T-Mobile (in $100 increments): $10/month, 100 minutes
T-Mobile (in $10 increments): $10/month, 35 minutes
Next Bracket, $20~25/month Comparison:
Page Plus Cellular: $25/month, 411 minutes
PureTalk: $20/month, 226 minutes
Boost Mobile: $20/month, 200 minutes - $25/month, 250 minutes
T-Mobile (in $100 increments): $20/month, 200 minutes - $25/month, 250 minutes
T-Mobile (in $25 increments): $25/month, 150 minutes
At a Glance:
Page Plus Cellular: Cheap entry with very low monthly minimum, minutes get really cheap with volume and will scale to high volume decently, texting rates are moderate, data is prohibitively expensive, must purchase in advance for better rates
PureTalk: Cheap entry with modest monthly minimum (that is probably in line with average low volume usage), minutes get cheaper with volume but not that cheap, minutes scale down in price automatically, texting rates are the cheapest, no data is available
Boost Mobile: Cheap entry with very low monthly minimum, minutes are always the same price and will not scale with volume well, texting rates are the most expensive, data is very reasonable and affordable, since amount added is not linked to value added can pay as infrequently as you like (when ever balance dips low or every 90 days)
T-Mobile: Most expensive ($100) entry but low averaged monthly minimum, monthly minimum can be trivially after first year, minutes can be very expensive if bought in small increments, lowest per minute rate ($0.10) is in line with basic rate of other services, texting rates are modest, no pre-paid data is available
Con Haste Conclusion (from phones on this list):
Check coverage areas first for obvious reasons
If you use data, Boost is your only choice
For an emergency only phone, T-mobile is best
With such varied methods of billing I'm not sure if there is a clear overall winner
Disclaimer: Data may not be completely accurate as I compiled it pretty quickly
My personal conclusion: I have no idea which one is best for me