Thanks, Robin, for getting back to me so quickly.
I used the calculator to determine that with my equipment the SA200 was the better bet. Your advice: “On telescopes with a larger aperture and a longer focal length, the dispersion of the SA100 can be insufficient to achieve the best results.” tallied well with my set-up — a 0.4m f/6.5 Dilworth with a SX imaging train. Plugging the relevant numbers into the calculator seemed to bear out that advice.
I will check out the other links too.