Which one will you buy?
Is 128GB really necessary?
It highly depends on your use case. Seeing as the 32GB is WiFi-only, you're likely to be using it in a place where there is WiFi. Given this, unless you are installing a lot of games or hefty apps on it, 32GB is fine for watching a bunch of movies and media given that most pay-to-own video services (including iTunes and Google Play) will let you stream movies and TV shows to the device without it taking up storage long term.
However, if you're doing a lot of media creation with a lot of powerful apps, yeah, you'll probably need 128GB.
Personally, I have a 128GB cellular mini 4 for when I'm on the go, and a 128GB Air 2 for when I'm not. If I were to get an iPad Pro, it would live on my coffee table and probably only be used for the iWork apps, and Hearthstone. Any media playback needs could be streamed from the internet, making the 32GB model more than enough. If I wanted it to be my flagship iPad, I would probably go for the 128GB model. That being said, I do feel like it's too big and too dissimilar from the other two iPads at this point in not-so-positive ways for me to want to make it my flagship iPad.
it depends on how you are going to use it? personally i will be putting a lot of movies on mine so i went for the 128, i would always get more space than you think you need if you can afford it.
Ant
If your movies are from iTunes, Google Play, or Amazon, you don't have to store them locally to play them if you are connected to a WiFi network. In the case of Google Play and Amazon, you just need to be somewhere there is an Internet connection; there is otherwise no storage requirement at all so long as you are online. In the case of iTunes, in addition to the WiFi connection, you need the space that what you want to stream would take up, but that frees up as soon as you're done streaming. Just an FYI.
Otherwise, I agree; always better to get bigger than you think you'll need just in case (as it's not like that sort of thing is upgradable).
32GB would be perfect given the cloud stuff these days!
Imagine how nice it would be to have LTE on the 32gb model..... :-(
It depends on what "cloud stuff" you use. Yeah, if you're streaming movies from iTunes, Google Play, Netflix, HBO, etc., and just using things that tie into iCloud Drive, Dropbox, OneDrive, etc. and not loading a bunch of games or space-heavy apps, then yeah, 32GB is perfect.
As for LTE, carrying around a cellular 9.7" iPad can really be cumbersome sometimes. Doing so with a 12.9" iPad won't be fun. They only put out one model of cellular iPad Pro because they knew that the people that needed it WOULD REALLY NEED IT. Otherwise, for cellular, the smaller, the better.
64gig lte for 929 would solve all my iPad pro worries!!!
See above. Cellular isn't always optimal on the bigger 'Pads.