9.0 VACUUM FULL vs. ALTER TABLE?

I understand that 9.0 will have a new implementation of VACUUM FULL that follows
a rewrite strategy like CLUSTER or ALTER TABLE.  What differences will remain
between VACUUM FULL and a no-op ALTER TABLE that rewrites?  Will there remain
situations in which to prefer the latter, or will it essentially boil down to
two different spellings of the same request?

CREATE TABLE t (x int);
VACUUM FULL t;
-- versus
ALTER TABLE t ALTER x TYPE int;

Thanks,
nm