35 mm (135 Film) / Half Frame

Till today I have NOT owned/used any 35 mm (135 Film) / Half Frame format camera.
So the following is not driven from own experince.

(My) Definition of 35 mm (135 Film) / Half Frame format photography

Use of 35 mm Film, as being developed for cinema, with a picture size of ~ 18×24 mm.

Pros of 35 mm (135 Film) / Half Frame format photography compared to larger film formats

Cost:
The film material, development and archieve costs are only half compared to the normal 35 mm (135 Film) format.
Greater Depth of field:
Due to the film format, the depth of field is greater, allowing for a smaller aperture in comparison. Snapshots and macro shots benefit from this.

Cons of 35 mm (135 Film) / Half Frame format photography compared to larger film formats when enlarged a lot.

Film Grain:
The smaller size of the 35mm half frame picture can result in more noticeable grain when compared to larger formats, especially when using higher ISO films.

My Conclusion(s)