I have XTs on one bike and Zees on the other. 180/180 on XT 203/180 on Zee. The XT is an excellent brake – powerful, reliable and had no issues when I was in Spain last year on long descents. The Zee’s are a step up tho, they are insanely powerful, loved them in the alps this year and coming back onto my other bike definitely noticed a drop in power.
The XTs feel like they have a bit more modulation and for most stuff I ride they are more than adequate. The Zees are still a fantastic all round brake tho (if a bit heavier) so if it’s power you really want go for those.
I bought mine from Tredz (front) and CRC (rear).