On Google
Tonio+Kroger+Mann turns up
596
Felix+Krull+Mann turns up 2580
So if Google is a good
representation of the canon (its better than most), it suggests
Krull is more important.
However part of the
reason Krull turns up more in quizbowl is the
"Confidence Man" part of the title, which gives question
writers a way to link bonuses with other Confidence Men
in literature (particularly Melville), that Tonio
Kroger lacks.
-- dml