We love both -- but the K80 are our favorite in ceiling speakers ever.
We also have the new M80, and they are better in a lot of ways, but if you want a more full range sound, the K80 seem to do a little better with that. There is something so musically satisfying about the K80. At low volumes they are engaging even just as background music. We have sold and installed hundreds of them and we regularly get unsolicited feedback from people telling us how much they love them when used around the house.
The kef are awesome as well, but we are really crossing our fingers that they release a new meta version to get them more in line with the modern voicing KEF has which is quite a bit better than it was in years past. The Bass extension of the KEF is impressive for sure too.
If you have any questions feel free to reach out to us as we are very experienced with both -- but if you have a local dealer you are working with that you're happy with, we are happy to give our advice either way!

