Oddly, I rode Stealth the other Thursday, then Rita on the Friday.
Rita looks and feels faster, but Stealth's is more prolonged.
You are right though, and Rita's acceleration dies very quickly, whereas Stealths keeps the pace up. I think that maybe the faster acceleration isn't all it's cracked up to be, a longer acceleration is actually better?
I am with UC though, the layout on Rita is what makes it better, but I don't really rate either ride particularly highly (they're good, but not great). The speed Rita takes the hills is bloody amazing, and it really slams you about. Erm, though pain isn't always so good