[R] multi-class modeling

[array chip]

Hi,

Just wonder if someone could comment on using linear
discriminant analysis (LDA) vs. multinomial logistic
regression in multi-class classification/prediction
(nomial dependent variable, not ordinal)? What kind of
difference in results can I expect from the 2 methods,
which is better or more appropriate, or under what
condiditon should I used one instead of the other? And
is there other methods I can try?

On another note, if I want to use logistic regression
using multinom() in package nnet, how can I address
the problem that each class of the dependent variable
has an unequal prevalence? In lda(), I can do this by
using prior argument, but there is no similar argument
in multinom().

Thank you!