Susa review seqmenus
This paper compares sequential and simultaneous menus with a user study, they declare the simultaneous menus faster.
Example of simultaneous menu can be found at the cancer by state visualization (check the viz4all review for details)
The finding is that simultaneous menus are faster, but the only significant data they have are the estimated advanced user speed based on composite of 3 users which I do not find very reliable. (the rest of the data has too much error).
I do think that for our case simultaneous menus are a better choice but not necessarily for speed but for clarity and reducing memory load (a similar argument to flamenco)