I bought today Xtrfy M4 and compared it to Kone Pure Ultra:
Human Benchmark: Roccat KPU with zero debounce activated vs Xtrfy M4 result: Xtrfy is about 10ms faster.
Xtrfy M4 has better, lighter, still crispier clicks.Tbh they both have a little bit awkward shape but I personally don't have a problem with these. Xtrfy is bigger tho and KPU feels more natural for my grip because it is smaller. (my hand is 18cmx10cm)
Id say also that I prefer Xtrfy size/shape over Zowie EC2. Xtrfy has really good mouse skates straight out of the box.
Xtrfy build quality is a little better than KPU. Buttons are that good. No extra sounds or movement with buttons.
Overall rating for Xtrfy M4: 4.5/5. Id give 5/5 if it was smaller.
(btw I love these M4 buttons and clicks, best Ive tested with any mouse so far)