I'd suggest perhaps get the 3G, as it has additional GPS chip which some apps need in order to work on the device.
I upgraded to the 3G model when it said on the screen of the wifi one something like "Foo app cannot be downloaded to this device as it uses GPS which this device doesn't have".
Though it's only a few lesser apps with me, I decided I also wanted the freedom of not tethering. Additionally I didn't want to lose my unlimited (no tethering allowed) iPhone 5 plan, by having to swap to another newer limited data (tethering allowed) version. (Though the price is going up for it next year by c.60p/month O2 have advised me recently — shock horror, blame inflation!).
PS. BTW, I went with a Three plan, as they have ones that allow you to use the data over THREE months, rather than all the other carriers that only give you your data for a month, before you have to re-pay for it again — whether you used it or not. Seemed best for my usage.
