Is height or reach more important in boxing if you had to choose between the two?

Height is often irrelevant. It's actually harder to punch down on someone. You lose power that way as well.

Must be why canelo lost he had neither

Height and reach belong together

Height can work for or against you to be honest. Look at how takam fights, his (lack of) height is used to increase his awkwardness/robustness. Reach on the other hand can help you control the jab ; its hard to see a situation where having better reach is a disadvantage.

reach 100%. height can actually be a detriment you provide a bigger target and hit the ground much harder if/when dropped...

Assuming your opponent was equal in footwork, timing, power etc. I think having more reach would give you the advantage. In theory you’d be able to touch them before they could touch you.

Height is more important to me; at least if I get knocked out I can still tout being taller as a moral victory.