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I spent far too long riding shitty cheap Shimano cable discs whilst I weighed up the pros and cons of Avid vs Spyres. I've only ever ridden Spyres briefly but I wasn't blown away by them. They're also much more expensive and require a reasonable amount of maintenance (for a cable disc - compared to a BB7 which requires near enough zero). Plus BB7s seem a lot more robust.
Anecdotal but I've only ever changed pads in BB7s in the shop, wereas I've had at least one dead Spyre, despite seeing far fewer of them.
I'd just go for a TRP spyre set. Those are a lot better than avids..