A:Answer The WiFi is always faster, and is unlimited.
The 3G,does have a limit, in both speed and total amount per month, but it's pretty high, not likely to hit it.
Use WiFi when it is available.
The 3G is for when you are not in WiFi range.
This is very nice, so you can browse and download as you move around, and when in remote locations.
I download a daily newspaper where ever I go, on the 3G.