When I reviewed the 12.9-inch iPad Pro, I made a short comparison video showing import speeds using the old SD card adapter and the new USB 3-capable one. Transferring 1.5 GB of image files took 30 seconds via USB 3 and 2 minutes 20 seconds via USB 2. That’s the actual data transfer; just moving image thumbnails so I could preview the photos before importing took 23 seconds via USB 3 and 1 minute 16 seconds via USB 2.
That effectively means that when you want to transfer photos to the 9.7-inch iPad Pro, you need to also come up with something else to do while that’s happening, because it’s not going to be quick. (And the 9.7-inch model also doesn’t benefit from the fast charging feature in the 12.9-inch model using an Apple 29W USB-C Power Adapter and a USB-C to Lightning cable.)
It won’t be a deal-breaker for everyone, but it’s an interesting wrinkle.