Sigma 30mm vs Zeiss 24mm

Yes.

With regards to your initial query: I have the Zeiss 24 and the Sigma 30. (The only native e-mount lenses I have FWIW.)

IME the Zeiss is more versatile, has more character and I'm really starting to feel that Zeiss "snap" some folks rave about so much. It just keeps growing on me. I really use the extra speed, width & close focus ability a lot.

I thought I might ditch the Sigma 30 but I really love it for what it does. I've found that for many landscape shots, when the target scene is a little more boxed-in, it is ideal. (It gets a much more detailed capture than I'd get, cropping from 24mm.) For me it has yielded a disproportionate number of landscapes bound for printing and framing.

I often roam with just the 24mm and leave the 30 at home but the reverse is not true, so I suppose that answers which one I would keep if I could only keep one.

HTH