What is your intended use of the tool? Will you be using it to supplement a laptop/pc or in place of one? If so, I'd lean surface pro. The biggest difference is in the OS. The Surface Pro runs Windows 10 which enables you to run the full suite of software that you've probably grown accustomed to.
The iPad Pro runs iOS10, so you will be limited to apps that are available on the app store. And yes, Excel and Word are available on the app store but they are severely neutered versions that lack the full horsepower of the traditional versions.
I am an avid Apple user (phone, watch, ipad) but it would be hands down Surface Pro for me if I were to use it as my primary device for work. Apple's devices are very slick but they are, in my opinion, best suited for consuming media and content rather than producing it. As an SM you need to produce your full suite of documentation each production and it's my opinion the iPad just isn't there yet.