I have a Dell Precision mobile with 16gb of ddr3-1333 ram. Would it be better to upgrade to 32gb of ddr3-1333 or 16gb of ddr3-1600 (max memory is 32gb of 1333 and 16gb of 1600)
Both memory speeds have CL-9 latency
Do you really need the 32gB of memory? If yes then go for it.
If your usage is close to 16gB then only go for the 1600MHz cards. Honestly going from 1333MHz to 1600MHz won't provide you with a big boost.