Wifi is a wireless network that connects to the internet. Although a few places charge for WiFi, it is usually free, but not always available. Cellular service is usually available, but it always comes at a price, and the price usually depends on the amount of data you are transmitting. Using cellular for voice and texting is low volume and therefore relatively cheap, but the rates for data can be quite high depending on the volume. I would definitely pay the extra $100 for the ability to use cellular, even if I didn't need it right now, because as Prism pointed out there may be times when WiFi is not available and you want to use your iPad to connect to the internet. However, be sure to look for a cellular service that fits your needs. You may want a pay-as-you-go plan rather than a contract. And if free WiFi is available, you will probably want to connect to it rather than to cellular.