I've used a 9 for a while now and it's my favorite woods tool ever. Handled a 4 at a store once and didn't care for it. On the plus side the guy working the counter hadn't picked it up so he handled it a bit after I gave it back and he said he was going to have to buy one.
You need a BK9. You can't not have a 9.
You need a BK9. You can't not have a 9.