How to choose an executable format?

[TheCanterburyPanther]

I've began researching for a hobby project where I design an OS and development tool chain together* and read that PE is the standard format for UEFI systems. That seems like a time-saver as I would only have to support the one format but there also seems to be many people who prefer ELF.

So, how wide spread are the effects of format?

[Octocontrabass]

I use ELF because it's the format my tools work best with, on all of the CPU architectures I'd like to target.

I can't think of any compelling differences between ELF and PE other than that, but I'm sure that's just because none of the other differences matter to me.