I just recently switch from Fuji mirrorless to Sony full frame mirrorless. Here is my observation when I compare those two:
Picture quality: For portrait, it's about the same. If anything Fuji has better colors. For night, landscape
Response: a7 is much much better
Autofocus: a7 is much much better. More focused pics when I get home and download them in my desktop.
Manualfocus: a7 is better and quicker.
Lens options: Fuji has many, many more options.
Build: X-Pro1 is solid. a7 feels plastic.
Feel: X-Pro1 feels much better in hands.
Portrait (still): X-Pro1 because of the better colors
Portrait (moving, babies): much more success rate focusing with a7.
Ergonomics: a7 can customize however you want. X-Pro1 has more manual dials but not as customizable and usually takes longer setting up.
Reliability: a7 is better.
Battery life: a7 is terrible