I ran some tests with a function that did nothing but recur/drop on a sequence. There was no speed difference between a vector, a LazySeq (previously evaluated), a PersistentVector and a PersistentList with a million elements. I tried it with ten million and it was 400 times slower with both a LazySeq and a PersistentVector. Attempting to make a PersistentList from the 10M element LazySeq with 'into' resulted in running out of heap space. I did not try again with more heap space allocated.