After all, both are holy and have been accepted in the tradition as correct and true, so how can two truths contradict one another?

There are disputes in Jewish law and in thought. This touches on the general question of how to relate to disputes (“these and those are both the words of the living God,” etc.). In my opinion, one is right and the other is mistaken, but both are legitimate. Each person should choose what seems more reasonable to him. Sometimes there also isn’t really a dispute, but rather a description in different language of the same matter, or of different aspects of the same matter.

Just out of curiosity, I assume you chose the Maimonidean side in the context of this dispute?

I don’t generally choose sides—that is, adopt one sage’s approach across the board. Each topic should be considered on its own merits. In general, I do not deny the existence of spiritual worlds and sefirot, whether as metaphor or as reality. But certain explanations in Kabbalah seem dubious to me. I don’t think all of this came down from Sinai, and there are many additions rooted in the reasoning of various sages, and those can certainly be disputed.