There really shouldn't be a comparison, as they are two different devices.
The iPad is a tablet. For all of it's strengths and weaknesses, that's what it is. Not a powerful as a laptop, more useful than a phone.
The surface line is somewhere between a laptop and a tablet. So it has compromises for both form factors.
I honestly can't see the point of debating between the two because they are meant for different purposes. For consuming media, light office work and ultra portability, you'd be fine with an iPad. But if you need to run full windows and apps, or require a physical keyboard, or need a USB port, then the surface is excellent.
I couldn't do my job without my laptop, but I've found when I travel outside of work, I never bring my laptop. The iPad does everything I need in that scenario.