FWIW, I think FORMAT-SYMBOL is almost always preferable, but I admit SYMBOLICATE is a classic of sorts.
for the record, cffi is full of these:
(symbolicate '#:foo- name '#:-bar)
which looks like this using format-symbol:
(format-symbol t "~A-~A-~A" '#:foo name '#:bar)
which is much more verbose for this kind of task. so, i think they both have their own places where they are are useful.