I know people discuss the timbre being a bit different between them, but I don’t particularly notice that too much. More than that, fit is different.

I have the se846 which is fully BA drivers, and they are totally sealed (no vents). You can feel the pressure when you pull them out of your ears. It creates a certain amount of sound just from that.

I also have the timeless AE which is a planar. It doesn’t seal the same way, and feels a step closer to headphones.

The only headphone I listen to music with more than almost never is the HD600, so that’s my reference.

They don’t sound the same to me in terms frequency, but I think the sensation of fit and venting are more noticable. The BA have high passive isolation, and also create pressure from jaw movement due to the seal. It also has a base sound like earplugs. The planars can be worn loose and allow the world to sound semi normal at baseline.

I dislike anc except in very high noise situations, so the earplugs effect of the BA is useful sometimes, although I just use airpods p2 for most situations where I would be in a noisy environment.