I prefer anamorphic for most anything I want to be handsome. There’s a certain feeling about it that makes the reality of cinema dirtier; the lines aren’t so straight, the textures aren’t so clean, the aberrations are sort of the point and a huge part of the charm. Anamorphic at 24.0 FPS with great production design and lighting simply screams “cinema!”
However, for certain projects spherical is more appropriate. Jurassic Park is 1.85:1 spherical because they needed the height to accomodate the tall dinosaurs. Spherical is cleaner, tidier, neutral. They can admonish the visuals in post without worrying about lenses that have too much character. Spherical lenses themselves are usually lighter and smaller than anamorphic ones. Spherical is easier to work with in post, especially for broadcast. Spherical is also not as distracting as anamorphic.
But, spherical doesn’t have the je ne sais quoi which anamorphic has; it doesn’t have the juice that anamorphic does.
One isn’t necessarily “better” than the other, it’s actually all about which format is optically more appropriate for the project. I just filmed Gungnir in 2.76:1 anamorphic, and several other recent projects in 2.39:1 anamorphic (Pure Evil, and Obsession). Others I’ve filmed in anamorphic but saved and cropped for 1.78:1 because we still needed the project to fill a 16×9 screen, but it was anamorphic and had the look despite the lack of ultrawidth.
I am about to start prep on a horror film that mostly takes place in a car. A wide aspect ratio would be inappropriate for that. The claustrophobic nature of 1.78:1 is more appropriate, and spherical primes would yield a better image than a cropped anamorphic one. Things to consider.
In general: I prefer filming in anamorphic for pretty much everything from music videos to feature films. Spherical is usually reserved for broadcast and reality work.