Both the XT1 & 2 have on sensor PDAF. The GFX will have CDAF only, but cameras like the SL have shown that having CDAF doesn't always mean having slow AF. You lose great tracking though, that's for sure. OTOH CDAF is extremely accurate generally, which is important for a 50mp camera. Nikon's and Canon's have faster AF than mirrorless cameras, even those with PDAF. The Leica S's, Hasselblads, Phase cams, and Pentax cams do not. Pentax has the best of the mirrored AF systems because it has multi points, but given that multipoint system was taken from their APS-C line up, the spread is laughably small. None of the above out-perform the original XT-1 in any way. It's not magic, and it's no D5 or 1DX, but there were few situations in which the camera would simply fail or frustrate you.