I made my first apron with vegetable tanned leather. I found this to be too stiff and uncomfortable. Every time I bent or sat down, the leather did not want to do the same. I thought it would break in in time, but it never did.
I made a second apron with the same pattern, but this time I used a soft 6/7 oz chrome tanned leather for the body. This one is comfortable, bends with me, and I wear it exclusively over the vegetable tanned.