I've got 3 different tires/wheelsets I'll be using this year. My all-rounders and schwalbe racing ralph tubulars, then I've got clement pdx tubulars for the mud, and schwalbe sammy slick clinchers for grass crits.
That said...I used the sammy slicks while I was lapping on a 90% grass course that was crammed into a small space (lots of tight turns) and wasn't super happy with how they cornered. Though they rolled easier, when I switched to my tubular racing ralphs I was much more confident in the corners and my laps were about 30" faster with a lower avg power. After that, I'm really trying to figure out when I'll be using the semi-slicks!