It depends on whether you prefer a straight microprism or one with a split image as well. I like the split image in there because then I have multiple options...if I have lines in the image, then I can line them up very easily to get great focus with a split image, but if not, you still have the microprism. All in all, I prefer a smaller microprism than the 13mm, as I felt that when it was that large it got in the way of my view in the viewfinder. I felt like I was looking at the microprism rather than at what I was shooting...the normal sized ones like in the R9 or older cameras like the R6, Canon F1 and T90 never gave me that feeling. I also prefer the horizontal split image, rather than the diagonal one.
All in all, it is about what you are used to, and what you prefer. And, as you probably remember, I returned my brightscreen. Jim is going to see if it was malfunctioning, and if that is the case, I will certainly be back to withdraw my negative comments about it. If not, well...they stand as they are now.