Having shot several weddings while using both XT1 and XT2 at the same time, the differences (all be it small) are pretty obvious when I'm bouncing back and forth.
The faster performance of the XT2 was immediately noticable for me at the first wedding I took my XT2 to. The faster response of the shutter button first grabbed me. The XT1 seems a bit slow now. On paper it may be a small amount, but I immediately noticed it. I only ever use single point autofocus so I didn't notice too much of a speed increase on the XT2, however love the focus joystick to move my focus point around.
Dual SD slots are very good for peace of mind. I have XT2 slot 2 setup to backup slot 1. I've never had an SD card failure yet, but knowing there is a backup happening as I shoot images I cannot shoot again ... it is a great peace of mind.
I find the Velvia processing of the XT2 to be better than the XT1. The XT1 over saturates a bit and is noticeable if used on people when they are shot close up. The XT2 Velvia is really nice for everything.
I do shoot video at the odd wedding (if they include it in their package) and the video from the XT2 is excellent. I'm really happy with the quality.
In my experiences over the years we cannot simply compare a 16MP image to a 24MP image when comparing noise (which seems to be a big concern for some). Take the 24MP image and resize it to 16MP and then compare 16 to 16. I expect in that case the XT2 will match XT1 and in some cases exceed it. This is something I learned and help me have a bit of perspective when I migrated from 10MP through 24MP Nikon cameras previously in my photography career. When I compared D3s 12MP image to D610 24MP images ... the 24MP had more detail at base ISO, but once the ISO started to go up 24MP had more noise. (Research the details on the 36MP D810 and you'll see the noise complaints of those that go a few stops above base.) But when I saved the higher ISO 24MP as 12MP and compared ... I got a better one-for-one comparison and saw the win for the 24MP source.
Don't know if that will help OP or not ... ?
Edited by Adam Woodhouse, 10 January 2017 - 05:13 PM.
TWO Fujifilm X-T2's + ONE X-Pro1
16mm/1.4 | 35mm/1.4 | 10-24mm/4 | 16-55mm/2.8 | 50-140/2.8
Flashes: Fujifilm EF-X500, iNissin i40 and two Yongnou 565's
Classic Lens Adapters: M42, Canon FD, Nikon and Minolta MD