Sorry about that! I'm a complete rookie with the new 'system' and UI on MR
I'm in the 128GB camp and like my iOS purchases before, having it but not needing the space ...especially initially in today's world and App Store options ...vs the alternative, needing but ain't no way you're going to be adding more in the future - but not having is an ugly predicament. I'm not a huge 'gamer' per se, but @ 44 and with a ten year at home, I'm reinvigorating my interest in gaming a bit and enjoying iOS as well as Android mobile gaming (I'm ambidextrous

). Not to the extent it's hogging a helluva lotta space ...but games are large. Decent productivity apps can be big (2-500MB) like the MS office suite, Adobe's mobile extension of The Creative Suite, even the <artsy fartsy> type painting, sculpting, free hand & creative apps are getting bigger and bigger
I got my iPad Pro Thursday of last week. I set it up on Friday evening after work (my carrot, hadn't even unboxed it yet) as a new iPad. Fresh, and without the extras I've been toting around on my Air 128. With the 12GB model, you're alloted 113GB for yourself, apps, media, et al. I've got 79.3 open, a total of 33.3GB used. The 32 if following the same measure (10% decrease in space from 32GB), you're looking at possibly 29GB to work with.
The iPad Pro is phenomenal, I wasn't sure I'd keep it but I'm 110%, completely sold. It's incredibly fast, sports a gorgeous display, and I've yet to see, much less use a 'Pencil' or the new keyboard. In fact, I'm not going to buy the keyboard at all. I'm going to grab a pencil but the built in iPP K/B is identical to my rMBP/iMac, Apple or anyone else's traditional keyboard. With shift keys, commonly used punctuation and 1-10/associated secondary keys accessible by still hold and slide up or 'shift'. Bold, italics, and underline, along with undo/redo, twin number and shift keys ...it's a whole new experience typing directly on the iPad. I'm not pecking out 85wpm yet, but I'll bet I can knock out 45-50!
Everything about it is over the top and built to last. It's doubling the performance envelope of my already wickedly quick Air 2 and iPhone 6s+. Not that it's noticeable right now but as time progresses and developers develop software that's utilizing 4GB of RAM, the insanely fast processing both computationally & graphically --- those AAA apps, or "Essentials' will only continue to grow. As will your images and/or motion capture files if you're planning to edit or manipulate stills/video of 12+ megapixels or 4K capture --- surely if you're into these hobbies, 128 is the only way to go IMHO. That said, if you're buying the iPP as an extra large iPad for consumption; video, music streaming, podcast listening while surfing or primarily as a document tool, 32GB is going to be plenty. I'm ignorant to the price difference as I wasn't at all interested in the 32GB model. But if it's the typical $100 bump, don't think twice. If it's >$150/$200, and you're experience with 16/32GB of storage on previous iPads or iPhones or smart {insert device here} has been pleasant without aggravation or constant juggling of the apps and media and books and magazines to suffice yourself due to storage limitations, it's a C Note (I'm guessing) you'll forget about in a week. And in a year, you won't be kicking yourself for saving the hundred bucks by 'betting low'.
I've been there, done that and it's miserable.
I didn't justify the 128 knowing I wasn't going to be buying the keyboard but it's a very nice surprise indeed. I suspect the upgrade price from 32---> 128GB is similar to the keyboard upgrade/peripheral. If that's the case and pardon the pun, but like me you don't need a keyboard case (mine is naked but the iPad cover, they don't make the full cases any more and I'm not going to pursue any more coverage...as the cover is perfect as a handle and screen protector when I'm not using it. It's too damn pretty to cover up the back!
So, again, if you don't have to have the $150 case or tote, you may be surprised at how little it's needed. I've owned each iPad and all have had cases. Usually more a function of handling with one hand than anything. I've also covered my iPhones --- but since the 6/6s model drop, I'm content with the Apple leather, open face, camera protrusion eliminator case. Perfect grip, thin yet elegant and casual or dapper, they nailed the cases this round too.
Sorry for the novel. I'm at work, bored and typing this on my iPP! (Keyboard free!) as well as my lack of interest or knowledge about the 32, but IMO... If you're gonna pull the trigger, empty the clip. You won't regret it. This is hands down the very coolest thing on planet earth!
...one con that I've found, the only one I'll add ...as mine's never crashed or slowed I glitched before, during, or after charging as some others have reported... Mine is flawless performance wise but it's large. It's not heavy, it's well balanced and the opposite of cumbersome. I can easily hold one handed (thanks to the Apple Cover) and use the other hand to manipulate it... But eventually the day will come that I need a carrying case/tote/ManPurse to travel with it. I'm not anti Murse but I'm not familiar either. Nor excited about the prospect. Maybe not. Thinking out loud, as I made it to work just fine without today!
Good luck n Happy iPP'ing!
J