I've grown to like 6.5" x 8.5" plates. I started out doing them in wetplate collodion with a modified 8x10 film holder. The largest standard plate that fits in the modified holder is full-plate. Plus, when cutting glass for ambrotypes I usually started with large glass sheets that I'd size to full-plate sheets and then cut into 4 quarter-plates for use in smaller cameras.

It turns out I can also just barely hold a full-plate glass straddling it across my extended fingers. This helps a lot when sensitizing plates and loading the special holder. 8x10 is just too big.

I also use 10x12 for similar reasons. Those plates will fit in a modified 11x14 holder.

I never really liked the 4x5 or 8x10 aspect ratio preferring to print 5x7 or 11x14. The latter two formats comprise the camera formats I most frequently use now. Another reason for the use of 11x14 ULF is that it is the smallest camera format where a life-sized head projects comfortably on the film.