I haven’t ridden the SR/F, but I rented an SR/S in Phoenix and rode about 200 miles. I expected to like it a lot more than my SR, and was surprised to find that I didn’t. It handled more confidently and had more power, but I preferred the SR’s flickability, more relaxed riding position, greater range, and less interventionist software.
When the battery capacities edge above 20 kW, I might buy a new battery instead of a new bike depending on what Zero does with their (D)SR bikes over the next few years.
Btw, SR/S foot pegs can also be fit onto the SR. I put some on mine and they made a night and day difference in my ride comfort.