I tried the X-T10 a few weeks ago (I work for a camera store) and found that ergonomically, I didn't like it as much as the X-T1. The grip feels less substantial and harder to hold onto. It's smaller but not so small that the size is a benefit over the X-T1 but for me, it's significantly less comfortable.
That being said, everything is nearly the same. I got my X-T1 months ago and have no regrets but it wouldn't be a very easy decision. It comes down to weather sealing and a larger EVF. If that's essential to you, buy the X-T1. If not, save your money and get a X-T10. It's 90% of the camera for 60% of the price.