The pumps all run at about the same pressure no matter 10, 12 or 16cc. The larger ones just move more volume. I would not let the pumps be any kind of deciding factor unless you are looking for a faster or slower speed.
We were briefly a Scag dealer and at the time I could sell the 35HP TT for right around $10k. Thats not fleet or anything. So 9800 fleet for 27hp Kohler seems high. Although the 27 Kohler was almost the same price as the 35 Briggs BB which made no sense to me. And I think the 35 came with a suspension seat, while the 27 did not.