The gpu on Surface book (if you buy the models with it) will be better than the ones Intel processor has, discrete gpu will be more useful for things that are gpu accelerated, especially when they use cuda. running 3d coat without cuda and with cuda makes a big difference for example.
Also the stability the base on Surface books gives, it's a laptop like one, and that's not something that that thin surface pro can do. so, some people will have problem about it and for example complain about how they can't put it on their lap correctly, or it feels awkward.
Also the surface book is not meant to be a tablet, it has the ability, but the battery life is not great as a tablet. but it needed a battery so you could flip the screen. but not really to be used as tablet all day.