excusing everything else, having a number of sms/minutes of call credit is SO much better/clearer/ more sensible than having a $$ credit. Given all the companies with $$ credit change the rates along with the credit limits, so you can't do a simple comparison between plans and the $$ credit is effectively meaningless.

"with our new $30 cap you get $10 trillion worth of calls! [small print: calls charged at $10 tillion per minute]" etc