If you are wishing to switch carriers from Cricket Wireless, you need to make sure your devices are unlocked.
If your devices are locked, make sure you have no outstanding fees on your devices and Cricket should have no issue unlocking it for you.
Once your devices are unlocked, you're ready to compare. Here's a set of comparison results for carriers 2 lines with BYO GSM phones
From these results you will able to compare data inclusions, minutes and prices to choose your best option.
If you want to port your existing numbers, make sure you do not disconnect the service linked with those numbers or it will be super hard to get that number back. Switch carriers first and the new carrier will handle the porting of your number.
If you are interested in purchasing a new device, remember choosing different ways to pay like through monthly installments, early upgrade or lease will make that super expensive phone really affordable.