In photography, let us consider the two subjects at hand:

1. The forms we strive to capture through photography (composition, the subjects we photograph, the shapes of things in our photos)
2. The idea or ideas we strive to capture and convey in our photos, for example the story in a photo, the message or moral/ethical takeaway in our photo, or our perspective in our photos.

Certainly both are important. The best photo as the photo that has a perfect hybrid between both notions! Beautiful form and forms, and also a powerful, impactful and moving idea or ideas in our photos!