iPad runs iOS software, Surface runs all Windows software, which is pretty much everything. It’s a full PC so you can run virtual machines, Visual Studio, Eclipse, and all that. If you need to do those things and also want a tablet, there’s no contest. The pen is also pretty damn cool. Also I suspect the higher end Surfaces are by far the lightest i5/i7 devices around, but I haven’t checked.
Really are quite different things. iPad/Android will be better as a tablet, probably. But I think the Surface Pen is cooler than any other pen.