Generally, there is no need to update the bios unless you are having a specific problem. What problem are you having with the system?
 
BTW, I only see version A11 for this model on the Dell website.

Any BIOS update simply enhances your BIOS. If you do intend on up[censored] your BIOS, you should generally update it with the most recent one. Dell is usually very good about having the most up-to-date drivers and such. If they suggest it, you should probably go ahead and do it, unless you have a good reason not to.
 
danleff is right with the fact that you really only need to update the BIOS if you are having a problem. However, I tend to update the BIOS before performing a large upgrade, like upgrading the OS.