I looked at all 6 outsides and 6 insides of the box, but I really couldn't find an indication of the speef of the Efke. Thanks for that one. I did notice that a shot without filter at iso 400 was rather thin.
I've shot both films once, so I can't really, truly compare them, but yes, the extra box speed would be a plus for the Rollei. I recall shooting that at iso 3-6 with 720 nm filter. The Efke I shot at about 3 iso is way too thin, and I read elsewhere on APUG that iso 0.75 or 1.5 is more in the right direction.
Grain of the Rollei is pretty good, I have a 30x40 cm enlargement from 35mm, and that looks fine.
A minus of the Efke or the way I process it is that the negatives are curly, curly, curly. But maybe that's just me, YMMV.