It has tended to be the case in my Samsung tablet experience that there tends to be more options when it comes to rooting and custom ROMs with the wifi varients vs. carrier tied lte variants. A personal example: I first got an lte AT&T Note 8 due to a promotion that they had at the time. That tablet ended up getting stolen, and I replaced it with the wifi version. Looking back, while it sucked shelling out extra cash for a replacement tablet, my experience with the Note 8 was MUCH better due to the ability to easily root it and a couple of really nice custom ROMs that are immeasurably better than the stock ROM, while I don't think there even are any ROMs that can be flashed to the AT&T locked-down version. I think it's rootable, but that's a relatively recent development for a device that's been out as long as the Note 8 (I think, there's a thread on the subject but I haven't looked at it).
Of course, the my take on the matter is really only relevant if you plan on rooting / modifying the device, or at least having the ability to do so, the wifi variant (or international lte version, I guess) seems to generally be the way to go.
I'm lusting hard after the Tab S 8.4, but I'm going to wait a while and keep an eye on this subforum mostly to see how development goes, and a price drop or sale would be nice when that starts to happen for these. If I end up getting this tablet (seems likely, the specs are pretty much exactly what I was hoping for in the TabPro 8.4), I anticipate that I'll end up getting the wifi version, even if I have the opportunity to get the lte version for the same price (I'm on T-mobile now and they had a promotion where they were selling the lte variants of the Samsung tablets that they had (which sucked when I checked it out) for the same price as the wifi variant with 2 GB free data or something, but not sure if that's perpetual). I now have a Note 3 and Note 8, and I really only use the tablet at home, but if I wanted to use it elsewhere I would just tether it to my phone with unlimited data, and all is right with the world
tl;dr IMO the wifi variant is the way to go so that your device isn't tied to any carrier and likely more modifiable, if you care about that. If this was a major decision that you were making that I completely solved and/or you're ridiculously generous, PM me for my address for pre-ordering purposes