A10X is ~30% faster than A9X in terms of single-core performance which is quite respectable. Goodness knows Intel would probably be very happy with an increase like that nowadays. Games are probably GPU-bound and graphics performance of A9 and A8X are very similar.
At this point in time, the A10X-based Pro 10.5 and Pro 12.9 are the fastest iPads available. They're good choices for someone in the market for higher end iPads
right now. If one can afford to wait indefinitely for a new iPad, well there's always something new around the corner.
Personally, I upgrade for at least one of the following reasons:
- killer feature to me (e.g. retina display)
- storage
- poor performance on my current device
- poor battery life or other hardware defect