Keeping for 2 years, 2nd hand hope as you’d lose nothing on them.
Keeping for 6 years, shimano, eventualy something will break, my piston seals went.
Keeping to let your kids inherit them (or at least relegate to the commuter in 6 years when padless magnetic levitation regenerative lazer brakes are released), Hope, my only problem with their brakes was a blown seal on some 8 year old C2’s, cost about a fiver to fix!
the rotor sizes make no difference to the brakes, its all about the calliper mounts to determine the size.
Kinda true, I’ve had a few recently that wouldn’t play nicely together for some reason, probably that some specify 180, others 183, others 185mm. If you keep hope rotors then best to buy hope adapters as they’d be more likely to work (IME).