Shimano are great, until they go wrong. And spares are non existant. Its either a new lever or a new caliper, assuming of course its available still.
I have a set of old style Saints that are 4 years old, have been used, abused, raced, uplifted and done whole seasons in the Alps which now reside on my girlfriends DH bike. Only now are they feeling a bit tired and in need of retirement. Looks like they will be demoted to her trail bike for the rest of their life. Other than braided hoses, and replacement pads, they have never been touched. Can't argue with that!
Considered the new Saints but they are seriously hefty brakes, (were at the time) very expensive & spare pads are hilariously expensive so were swiftly discounted.
I've been running the new Tech M4's on my DH bike, and the difference in power over the old Saints is huge. I also like the fact that you can actually buy spares for them should something go wrong. She will probably end up with a set of these also, for convenience and pad stocks. Considered the V2's but they are somewhat OTT, unless you have some extra padding to carry around, or can't ride/brake properly…