It may just be mine, maybe I have a faulty one, but I own the Surface Pro 3 and really dislike it :/ I bought it right when the 4 came out I think and really regretted not just getting an iPad pro instead.
To be specific, mines the i5 processor, 256gb, 8gb ram verison.
The fans on mine are pretty loud and the machine gets a bit hot with just a browser open. I've also had it freeze up on me a lot just running ps and a browser with a few tabs (5 Max).
Also if you're planning on using an external for extra storage space, the surface will need you to use a USB dock with it's own power source, as the surface can't provide enough dedicated power to access the external on it's own.
::EDIT:: I never work on anything bigger than like standard paper size - canvas wise and have had freezing occur D:
::EDIT 2:: On a positive note, the newest (or second newest???) Surface pen is REALLY nice once you deactivate win ink... They're $100 USD to replace if you lost or wanna upgrade one tho