It sounds like 85% of the experience for 40% of the cost.
And money is always a priority !
If you use your iPad for gaming and watching videos apart from content consumption, the four speakers on your Pro will create stereo sound and that is the single largest bonus of that thing versus an Air 2. Ability to use Pencil on the Pro, making it a venerable drawing pad you can often use for productivity or to pass time doodling, is another plus in the Pro's favour against the Air 2.
I sold my Air 2 last November, simply to get some money and wait for the iPad lineup refresh. Now, I will purchase the Pro 10.5, if and when I do it. With iOS 10, I had really gotten down to sending handwritten messages using my finger on Air 2 screen because of the way iOS would make nice graphic images of it, and having the Pencil means an added capability on Pro 9.7 and 10.5.
While you are quite right about the 85% experience, but I do find value in the remaining 15% and I am confident that since you do have it, keeping it would only serve you better if you are using that remaining 15% today. If not, then you might look at taking the Air 2, but it all depends on if you are saving really that much. That 15% (in my case and wants) is worth the value, because I used my iPad majorly as a video device and browsing and typing device, and then gaming. So, it was really a sad experience where audio was concerned.
4 speakers, 4GB RAM, Pencil support - that iPad Pro 10.5 is a real worthwhile tool to have in your arsenal/ workflow, if you have the desire/ need for what it offers more than the Air 2.
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Let me just add to this:
Aside from searching for a sale price in your situation, My Air 2 runs stellar since day one and iOS 10 only made it better. Before the new Pro's arrived, it was the best iPad to date and is still runs so efficiently and I refuse to sell my Air 2 (It's in mint condition) and it's one of those products you come across that just won't sacrifice performance. It's still my favorite iPad and I can't wait to see what iOS 11 can do for it. If you decide to purchase an Air 2, you won't regret it, even if the new iPad Pro supersedes it.
Only thing where an Air 2 did not do that good was audio while watching video. That sound coming from one direction just never quite sat well with me. Other than that usage (watching videos on it), that device NEVER slowed down and was a real powerhouse for as long as I used it before I sold it.