$900 more and the only difference is disc brakes? The premium over rim brakes should not be that high. If the rest of the build is similar then you are paying A LOT for that upgrade. I’d agree with what everyone has said above about performance difference. I’m always a slow adopter of new tech and I guess my feeling on road or TT disc is that it isn’t something I would go out of my way to get upgrade for BUT if I was getting a new bike it is the way I would go for all the reasons above.