That's not true. You only need to be on the same wifi network to do the pairing. After that, both devices just need to be connected to the Internet. But it doesn't have to be the same service. I have done this before. I just don't have an iPad with LTE so I have to wait until I get to a place that has wifi. You only need Bluetooth when you are doing handoff. Not continuity between an iPhone and iPad.
I love handoff between my Mac and iPhone but i would find the iPad to be clumsy.. also, do you feel that you can make it through the day on the Wi-Fi only model? I'm trying to decide between the two but since I can't add unlimited data through AT&T (but I'm grandfathered in on my iPhone), I think the Wi-Fi would suit just fine. Strong Wi-Fi at home but shotty at work.