For all practical intents and purposes they are the same. The real difference is the physical size of each and the age of the older card. You should be able to configure either to work with the cell phone and data cable. However, it would have to be a data capable of connecting to both the cell and the computer.

I hope this helps.

you need broadband which requires a NIC (network interface card) for voice. These are considerebly faster than dial up connections. If you mean the difference between an internal dial up modem and an external one, theres unlikely to be any differtence, both operate at an immensly slow rate However the one built in (the internal one) will be slightly faster, same goes for USB wireless sticks versus PCMCIA - closer to the motherboard the faster.

No, you cant use voip on a 56k line, the delay would be 3 seconds or so even with a fast connection speed. Its possible but not worth it in my opinion.

There is not much difference really, but the internal one is easily installed if you formated your computer, since it’s a built in device, it will be automatically identified, but the other modem cards would need an installation CD to identify them and install their driver …
the cell phone is a different thing though .. I didn’t get what you wanted with it ..