I don't like 64s for a couple reasons. First and foremost: I play with bands and the low notes just don't carry. Also, a newer player may find the lowest notes to be balky. Also, there is more chance for wind saver rattle.

I valve almost all my Hohner Big River and Hohner Blues Harps. I like being able to play the notes that are not otherwise playable (unless you can do the overblow/overdraw technique. I valve for these notes only and remember valved bends lower the note not raise like the overb&d thing.