I use the Verizon LTE network on my iPad pro all the time. When I'm on the train, when I'm travelling hither and yon. I don't browse/read/search on my phone (which I use for actually calling and texting people). Not saying that I represent a typical consumer but I certainly represent at least a cohort of 1 consumers :-).
I had a MiFi for a while (company purchased), but found it consistently had lower performance then the native networking of my iPad and it was easy to lose if I wasn't paying attention. Twice I encountered times when it wasn't charged when I needed it. On analyzing it overall I found that because it wasn't forced to be charged when I charged my laptop/tablet, it suffered from sometimes being missed when it needed to be charged. That the radio is by definition charged when the iPad is charged avoids that failure mode for me.
When travelling with my SPro4 I would sometimes 'hot spot' it to my tablet. Awkward but it works. In the inversion that I still marvel about the software availability on the iPad has always been better than the availability of software on the SPro4.
The SPro4 has a better (to my taste) drawing experience than the iPad Pro does. And both the iPad Pro and SPro4 are way better than previous stylus attempts on capacitive screens.
The iPad has a much better 'tablet only' experience for me, and a much worse 'docked' experience. SPro4 with a Surface Dock and a couple of UHD monitors is literally indistinguishable from the NUC i7 box I use as a desktop. There is nothing (yet) that I can attach to my iPad Pro to make it work like a Macbook Pro (I know I know, different OS, processor etc.)
As a result I create more in general on my SPro4, consume more on my iPad Pro. I travel with my iPad in my hand and my SPro in my backpack.
Clearly I have been unable to leave one behind and just use the other so there is some more convergence to go :-)