I just bought a 2015 i5-5257U MacBook Pro and a 2017 i5-5350U MacBook Air as Xmas gifts, both with 8 GB RAM and 128 GB SSD, within the last month. They were about US$360 and $325 respectively.
The MacBook Pro 2015 looks almost brand new. The screen and lid are perfect, as are the top case and keyboard, and the battery has only 29 cycles. The parts that give it away as not brand new are the bottom cover which has a few scratches, and the charger which looks used. I figure this thing must have had its battery replaced recently, because the unit itself was manufactured in 2016. According to all info I can find, including comments from forum members here, it's a legit Apple OEM battery, and the fact that the top case and keyboard look new makes sense, since they replace all three at the same time when doing a battery replacement. In any case, it wasn't used much, since the 128 GB SSD only has 4 TB and change written. I ended up replacing the SSD with an OEM Apple 256 GB SSD though, which I got relatively cheap off eBay. (I didn't want to go the third-party route for an SSD.)
The MacBook Air 2017 also looks almost brand new, with I'd say 9.8/10 cosmetics, although the battery has about 460 cycles. It was an Apple refurbished model from 2019 I believe. The 128 GB SSD only has about 9 TB writes.
I'm not a big fan of the MacBook Air's screen, but it's fine. The MacBook Pro's Retina screen is awesome though. In terms of performance, I could use either of these as a full time business laptop. The only deficiency I notice compared to my 2017 12" MacBook (besides the non-Retina screen of the Air) is the lack of 4K video playback. The 2017 12" Core m3 has hardware HEVC acceleration on board, which is necessary for decent 4K.
I am very, very pleased that M1 and M1 Pro/Max are such great machines, with M1 Pro/Max bringing back MagSafe and all the ports. I suspect the existence of those highly performant machines, complete with scissor keyboards and all those ports, is a big reason why these scissor-endowed 2015 Pros and 2017 Airs are so inexpensive these days, aside from their age. (For these gifts, I specifically excluded all butterfly models.)
One thing I've noticed though is that despite the fact the Pro has an almost new battery and the Air has a moderately old one, is that the Air seems to last longer when it is being pushed hard. This agrees with the
Ars review from 2015, which shows that for basic web browsing, both the 2015 Air and the 2015 Pro do reasonably well for battery life, but under heavy load, the Air lasts much longer. This makes sense because the Pro uses a 28 Watt TDP CPU whereas the Air uses a 15 Watt.
BTW, one drawback of the Pro is that it's a lot harder to replace the battery. As mentioned, Apple replaces the entire top case and keyboard when replacing the battery, because the battery is glued in. For this reason, it's an expensive replacement from Apple or else a labour intensive one if you do it yourself. In contrast, it's dead simple to replace the Air's battery. It's a separate part and it's held in just with a few screws. Because of this, if you get Apple to replace it, it's nowhere near as expensive as with the Pro.
