I use an SDB since my collection is worth greater than 10k. I would need one anyway for important papers, just got a bigger one to hold the coins. Be sure your bank is on high ground. May sound silly, but the bank down the street from me is in a floodplain and during a 100 year flood, all the SDB's were drowned. (Not where I have mine fortunately!)
Husband works for a bank and a perk is a free SDB so I'll be taking them up on that shortly! I think I can even get any size I want!