I love my 128gb iPad Air 2 as well and was randomly wondering the same things as you at first. IMO, I think it all comes down to Apple just wanting two have more than one kind of iPad to offer the masses, much the same way as they offer both the iMac and Mac Pro, MacBook Air and MacBook Pro, iPod (now just Touch) and iPod Nano's and Shuffles, etc. It comes down to Apple wanting to have more than one option (price point and more flexible options for people's differing reasons for using a device). Different strokes for different folks, etc. One isn't necessarily "better" than the other - it just depends on what you want to use it for and you decide which one is better for you.
Of course the shiny new thing is always touted as the next best thing but it's (usually) all subjective when it comes down to it.
I know this isn't what you were probably looking for but I had the urge to put my own 2 cents in. Hopefully someone else can answer your question a bit more scientifically.
Appreciate your reply man, your totally right. Not sure dropping £600 big ones on a 'pro' is sensible. The AIR 2 is great but suddenly the PRO appears and its "oh the AIR 2 is old now and rubbish". Human nature , its all marketing. I think its the AIR2 for me. The only attraction to the PRO for me is the A9x chip. So now the A8 is 'rubbish'. So the average blind consumer will think.
I don't take pictures or videos on an iPad. Most of my time I'm at home studying. I have a desk and chair with a macbook pro. The iPad is for internet use in bed, such as forums. Right now I'm sat in a big leather chair, PS3 and PS4 linked up to a 55" TV. So i think to myself 'does an A9x chip justify a 'PRO'... no. If i goto a friends house or a weekend away I can take my iPad with a really nice logitech keyboard.
I think I just answered my own question. AIR 2, wifi (can tether if needed), 64gb for £343. Thats a steal IMO. Combined with a 6s+ 64gb.
The average consumer hears the word "PRO" and thinks if they don't have it they are a loser. Its like 'i must upgrade my car to the latest model'. I think a majority of people are blind sheep or follow marketing as opposed to their true needs.
I think apple has become another tech company now, adding words like PRO. OK the pencil and its ability of use on the PRO will be utilised by some people for WORK purpose and productivity. How many people will buy this because they CAN?
Apple used to be about innovation, every product was ground breaking back in the days of SJ. What do we get now, an iPhone 6 that is more about Jony Ives obsession with design over use. Its not nice to hold, its slippy, the camera stick out. How is this productive? SJ would not approve of any of this I'm sure of it. We got the Mac Air and it was amazing. Where is the evolution? Its like apple is lost now. Did SJ approve the 5S? I cant recall.
Look at the case extended battery pack, what the hell is that about? It looks......****.
Im probably just talking rubbish and I'm sure many people here would disagree. Yes the new macbook (its clearly the Air) is nice, but its design>use. I still adore apple and the eco system. I could never not use iOS or OSX but I'm worried they will turn into an average tech company. We get a 1 hour even showing a few watch bands, a 5s casing with new internals. A mini pro. And waffle about health apps.
Steve Jobs... where are you. "One more thing..."
Im not bashing Apple. Ive had every iPhone apart from the 5. But since SJ died its all felt a bit 'stale'.
TLDR: Ive had too much wine.