You could go "overboard" and use large diameter, short lag screws, perhaps with a washer under each one. A pilot hole drilled for the lag screw will make the job easier and reduce blooming or mushrooming of the material around the lag screw.
The above item lists on the 'net for US$5.50 for 75 pieces, not a bank breaker. Unless you spring for the stainless version, expect some rust over time on the zinc plated/galvanized ones. Stainless might be a bank-breaker, though.
If you don't want to use large diameter lag screws, smaller screws with fender washers under each one will also provide a secure mount. Fender screws are larger in diameter than the average washer used on bolts.
Curiously, the above item happens to be available at the same web site for US$5.40 for 100 pieces. The same caveat applies regarding rust versus stainless steel.
Generally speaking, screws are going to be preferred over nails for ease of service and/or removal over time. Nails might not be quite as easy to install. Even a lag screw that passes only a half inch into the studs will have greater hold than a nail.