Well, I don't want to be in the position of arguing that the MBA is a better laptop because I don't know that it is and I don't care that much, just wanted to make a point that the difference isn't as black-and-white as you're making it out to be.
This seems to be a good review and raises some issues.
http://www.notebookcheck.net/Asus-Zenbook-UX305-Subnotebook-Review.136543.0.html
That's a really poor review because it tests a completely difference device with a 3k resolution, a pretty insane 3200x1800 resolution, that has a touch panel, more than any Mac except the new retina iMac and that device is non-touch and twice the size. It has a higher PPI than any Mac device and it's a touch panel. Of course its battery at that resolution isn't going to be the same as the non-touch FHD, one which is noted around ~10h. Not quite the MBA's 12h, but 10h is more than sufficient for a 13 year old who doesn't need insane battery for travel or work, better than the 11" or 12" Macbooks, and better than the 8h minimum OP asked for.
It's also a poor review because this model (which again, is not the model I referred to) is $270 CAD more expensive and more than retina, and is thus compared to the Dell XPS 2015, or the rMBP, whose contrast and color accuracy are all far better than the MBA we're comparing it to.
Same with performance, any comparison to a mac in that review is one compared to a rMBP, not a MBA. But in terms of performance, all reviews I'm reading say that it has runs perfectly fine. Remember, OP already says his kid isn't gaming on it and uses it for school, the chip in the Asus is a bit like the MB, fine for regular use but not for heavy gaming or e.g. editing large videos. And remember, it has double the RAM (and storage, but that doesn't affect performance) as the MBA, while still being cheaper, cheaper even than previous years' models that is.
Well, the Best Buy MBA might be last year's design but it might have been manufactured a month ago, so it's almost certainly not a year old. And there's not that much difference between the 2014 model and the 2015 model. So I would expect it to hold its value pretty well.
It doesn't matter. Would you pay $1800 for a new Macbook Air 2008 manufactured yesterday? That was the price they launched with. Of course not. That's an extreme example but it makes my point: value & especially resale value doesn't consider manufacture date first, it considers the models' date first. You're simply not going to get the same resale value in say 2016 on a 2014 MBA as a 2015 MBA, despite having been used just as long, that was my only point. Beyond that I agree a MBA 2014 will hold value pretty well.
Anyway it's besides the point, OP aims for a 5y+ usage, resale value difference on a 4gb/128gb 2014 MBA without even a Full HD resolution in 2020 just isn't going to sell very well, and certainly not much better versus an 8gb/256gb 2015 model with double the resolution.
You might be right about resale value for nice PC laptops. I have only resold nice PC desktops and I know that you're lucky to get $100 for a really nice desktop PC, where just the power supply or graphics card might cost twice that if you were to buy it new. I would be surprised if you could sell any PC laptop for any significant amount of money but I might be wrong. If you have personal experience then I'd be interested to hear it. I have bought and sold some used, ~5 year old MacBooks for significant amounts of money.
Yup, exact same experience for desktops. I usually get about 15% or so on my desktops back. Laptops, they do quite well. A $1200 laptop usually still sells for $300-400 years later. It might be less resale than a MBA, but not so much less that I'd throw a discount, double ram, double storage, thinner, higher resolution etc out the window for it. In terms of value you just can't beat the ASUS unless you value OS X a lot, and it seems OP's kid never used OS X much if at all which is why I'm mentioning the ASUS.
I'm not saying the ASUS is perfect by the way, or better than a MBA in every respect (performance for example, is a bit worse). Again I prefer my MBA. But for this particular person, with his needs (non-gaming, non-development, non-professional work, school stuff, internet, youtube, facebook etc), with budget constraints, without an express need for OS X... it looks like the ASUS is great value.
I mean just read a quick review like this:
http://techspective.net/2015/03/02/review-asus-zenbook-ux305-ultrabook/
It's a nice little device.
he tells me the macs last a really long time and that it would suit his needs better.
Compared to what? Those are relative statements. Compared to a $250 Windows laptop, sure. But if you put a $1k Mac against a $1k desktop PC, the PC wins by far in terms of value. The past decade or so, the opposite was true for laptops, in my opinion, Macbooks were better devices generally. But quite recently we've seen windows laptops deliver better value, too. And you can see that in models like the new 2015 models from ASUS and Dell. They'll last a long time, too, have better specs for a better price, and come with strong, thin and slick aluminium builds.
As for "suiting his needs better", it's fine to make a blanket statement like that but he needs to back it up. I just don't see how a 13" MBA is more suitable than a laptop that's thinner, with a 10h battery, with double the ram, double the storage, higher resolution, completely silent, that saves you or him over $100. It's up to him to convince you, I'm just putting out some alternatives to look at.
Anyway I mentioned the battery before. As for where to buy it, Microsoft Store Canada.
http://www.microsoftstore.com/store...-Signature-Edition-Laptop/productID.313368800
I'd recommend checking with a few big stores in Canada to see if they have one. It's always recommended to give it a try before you order.