How are you finding the Surface Pro battery life?
I have a surface pro 3 at work and the battery life is pretty abysmal.
I'm dropping about 20-30% about every 2 hours...definitely not as good as my iPad Air 2, but maybe around or a little under my 15" retina.
But that's with Bluetooth on (for the pen) and actively taking notes. I guess I see it as kind of a trade off - I can't look at a pdf/lecture/website in split screen on either of those devices, while at the same time taking pretty natural feeling notes.
Prior to this, I use to load the pdf on the 15" MacBook, and use goodnotes on the iPad. It felt pretty goofy and seemed pretty redundant.
Regarding power - I have the i5 with 4GB ram version. Only 128GB ssd, but it has a slot for MicroSD card.
Honestly, all I really use it for is school work - the processor is such overkill, but it handles everything I've thrown at it very well.
With the current preview sluggishness issue affecting retina MacBooks - it even handles large PDFs much better than my 15" retina. But that's a long time bug with preview that's hopefully fixed soon...
Its an i5 processor in a tablet form - so lack of power shouldn't be an issue (the MacBooks you're looking at are i5's...except for the 15").
If you're concerned about the GPU - then you're kind of stuck getting the 15" upgraded version anyway.