My workshop experience –
Avid – dont bother, you do get a few lucky ones though, most probably my fave in terms of feel, shape and power though when they’re box fresh with a good bleed
Hope – totally rebuildable/serviceable/easy to do but are never really good though, pretty rubbish actually, not worth the money
Formaula – pretty reliable, tight on pad clearance, just keep pistons clean
Magura – fine, service spares is only issue
Shimano – faultless and the consistently best performing, the odd duff set, not surprising the volume i’ve seen though. cant rebuild them though, but the way things have panned out though, the current deore are easily as good as previous XT