Slight focusing of question
I think one key topic which is missed is the ability to draw on the extra power supplied which can speed up charging. Now I'm not stating that this is a fact for the MBA but it has been shown that the 10W ipad charger will charge an iphone (especially while in use) faster than the 5W charger that comes with it.
A second minor key issue is the reality that size does matter in terms of efficiency. It is true that your MBA might draw a max of 45W (for arguments sake) but different power adapters will have better performance at different power outputs over their usable range. But in the grand scheme of things I really think this is a non-issue for this use case.
I think one key topic which is missed is the ability to draw on the extra power supplied which can speed up charging. Now I'm not stating that this is a fact for the MBA but it has been shown that the 10W ipad charger will charge an iphone (especially while in use) faster than the 5W charger that comes with it.
A second minor key issue is the reality that size does matter in terms of efficiency. It is true that your MBA might draw a max of 45W (for arguments sake) but different power adapters will have better performance at different power outputs over their usable range. But in the grand scheme of things I really think this is a non-issue for this use case.