I will always have cell on my iPad. I like having the option if I need it, and I use a month to month plan, so I only pay for it a month at a time. My phone is T-Mobile, my iPad is Verizon. When our internet is out, or during the last hurricane, I appreciate having cell on my iPad, and in my area, Verizon is either the only carrier on during big storms, or the first back online.
I have 64gb on my Air 2, which is enough for me. I have a lot of apps, few photos, not much music, and it's at 14gb right now. My last iPad was 32, same stuff, and if I downloaded 1 movie, I would have to be sure and delete it when I was done, or I would have problems with the next movie.
If you think you'll have a lot if music and/or videos, you could fill up 64 pretty fast.
If it is a choice, I'd want the cell option over more space, but only you can know how you will likely use your iPad.
I'm not concerned with resale value, the difference is too small weighed against how I want to use it, and my convenience, over the next 2 or 3 yrs.