Dear ULF shooters,

I've been contemplating a move to ULF for several years, and I've toyed with getting into various ULF formats: 10x12, 14x17, 8x20, etc.
Given that I finally have a good scanner, and it can scan up to 12"x17", I'm looking into shooting 12x15.
The dimensions are the same as 8x10, which I like.

My question is: is there an appreciable difference in image quality between 8x10 and a ULF format such as 12x15?
Or is it a negligible difference?

Some of you shoot ULF because you like to contact print, others because you like extreme panoramic formats, and carbon printing is also a practical consideration.
Those are valid reasons for adopting a ULF workflow, so maybe you haven't considered IQ as your prime motivation in using ULF. But why would anyone get into ULF if the dimensions are the same as 8x10 (or 4x5)?
I'm just trying to gauge the difference in image quality between 8x10 and larger formats; at what size does the difference in IQ become really noticeable?

My logical brain tells me 8x10 is the optimal format; that the trade-off of carrying larger cameras, film holders and lenses is not worth the small increase in IQ.

What say you, commentariat?
Thanks in advance