A little late to the party, but I'd thought I'd share my experience as someone with a home full of antiquated Macs that still manage to do everything I need.
The 2008 Mac Pro 3.2GHz 8-core I bought from Apple Refurb in 2010 is still going strong and is running El Capitan. All four HDD bays are loaded and I use this computer to rip CDs, DVDs, and process my photos and videos on.
I then copy what I want out to an external HDD which I use with my 2010 C2D 2.66GHz Mac Mini that I bought from Apple Refurb in 2012. The Mini runs El Capitan and is my main media centre, it's connected to my 50" plasma TV but I can also access its GUI through the Screen Sharing app on my MacBook. I play music through Audirvana+ with EQ filters, mostly LPCM up to 24/192 but I do occasionally play some DSD (DoP) when I'm auditioning DSD DACs and the Mini seems to handle it fine. I control it either using the Remote app on my iPhone or by using a bluetooth mouse (the latter obviously requires either my plasma TV or laptop to be on so that I can see what I'm controlling). I frequently watched ripped video content up to 1080p, Amazon Prime and Netflix on the Mini with no problems. It has however recently become a bit stuttery when playing 1080p/60 YouTube videos in realtime, but it usually rights itself after a few seconds. This Mini is also used to share my iTunes library and, more recently, mkv video rips with my parents' AppleTV.
The 2010 C2D 2.4GHz MacBook Pro I bought new in 2010 died last year. In latter years I used it daily to watch live TV and iPlayer through an external display. One day it just cut out and wouldn't turn back on, I probably ran it too hard as the fans were constantly spinning when piping video out to the external display.
The 2011 i5 1.6HGz MacBook Air I bought new in 2011 is still going strong and is still in daily use running High Sierra. I use this as my general purpose computer and have really pounded the SSD drive (frequently less than 10% free space left) but it still works fine.
Since 2017 the MacBook Air has shared duties with a 2015 i5 2.7GHz MacBook Pro that I bought new from John Lewis in 2016 at a price the was too good to refuse. Unusually it came with El Capitan installed and I've never gotten around to updating the OS. This is my best Mac and I treat it with kid gloves as I want it to last me a long time (I'm not impressed with the reported reliability/build quality of more recent MacBooks, though hopefully the M1 architecture heralds a new dawn).
I was very tempted to buy a new M1 Mini and give my 2010 Mini to my parents so they have a traditional computer they can use to access all of the content we've accumulated over the years. (I literally have tens of thousands of family photos and videos that are stored in traditional folder structures. I never had the time, patience or trust to load them into an app like iPhoto so, AFAIK, they cannot be accessed through the likes of an AppleTV). However, I was put of by the reports of an intermittent bluetooth connection on the M1 Mini, this is an essential function IMO that needs to work as intended. Besides, my ancient Mini still does what I need it to do, so why replace it?
I'm still considering buying a used Mini for my parents. The question is which year and spec represents the best VFM?