C3 is the one of the cheapest wifi phone from Nokia with a QWERTY KEYPAD. it has chat application preloaded. You can chat on your Yahoo id or gtalk id or from OVI chat. But it is not having 3G and only have GPRS and EDGE.
whereas E5 has all the main features of 3G connectivity to connect from sim card.

only difference in Nokia device and BB device is B2B chat. Other than that all features are there in Nokia at a better price.