A few things to consider
Fido and Rogers - use
GSM technology which means you can buy your own phone, whatever unlocked
GSM you have(and right bands at least one of either 850 or 1900).
If you go with Telus or Bell they use
CDMA, you HAVE to buy their phones. In Canada that is a huge drawback because for some reason we are sold phones that have been out on the market for at least 2 years.
If you go with
CDMA, then please go with Bell and not Telus. If i could I would use some colorful language to describe their contracts and phone selection.
If you want to buy a phone that is not at least two years old and go with
GSM providers, both Fido and Rogers are good. I use Fido because they are the only ones to use per second billing.
Hope this helps