For me, if I'm going to be using a device as a laptop, I want a solid keyboard. When we tried the SP3, I found that carrying it felt like carrying a laptop rather than a tablet. The iPad fits in my sling bag and other lighter bags I have. For the SP3, I had to get out my laptop bag. So the Surface gives me a compromised keyboard, without giving me increased portability. So unless the SP4 gets significantly lighter, I'll be sticking with the MBA.
Personally I don't find the MBA keyboard much better than the SP3 keyboard, I'd say it's marginally better. I do agree that carrying it is quite similar to carrying the MBA, although you could carry the SP3 around without the keyboard making it significantly lighter, not much heavier than the ipad air for example, and way lighter than the MBA.
I'm not disparaging your choice though, sounds like a MBA works better for you.