I've got both the larger Diva Cup (which is a bit too big for me
) and the smaller Mooncup by Keeper in Silicon.
For me, the Mooncup is a better option, as in addition to being a bit narrower, the silicon is a little firmer, which I think helps it "pop" a bit better. Also the mooncup has a longer stem at the bottom, which for me is an added bonus (easier to remove).
I guess it just really depends on exactly what shape and size you are.
Have you thought about maybe ordering online once you've worked out if the Diva cup is still the right size for you?
FWIW, I ordered both my cups online from the US as technically menstrual cups are illegal in Australia (not approved by the appropriate board or something). Bizzare!