It is hard to say what to do without knowing what you have there.
The first handsets were nickel plated. They worked fine in fresh water. However, due to a problem with a contractor that did the plating, there were many that suffered severe corrosion when placed in salt water. The earliest also had face plates that corroded.
The next version of the handsets had annodized aluminum cases and steel face plates. There are many people still using these without incident. However, there have since been improvements in the delrin case version (in the battery compartment and spring) that takes care of some issues that people were sometimes having with the battery contacts and corrosion in the battery compartment. (I never had these issues though I was meticulous about cleaning the contacts and using contact lubricant.) Also, there is an inexpensive upgrade available for these handsets because the firmware would cause oxygen to inject everytime that the unit boots up, which is a problem if you have a battery or contact issue (especially in deep water).
The most recent version has the delrin cases plus the ability to use the secondary for decompression. There is also a battery indicator and alarm. The new cases are lighter weight and a bit smaller, too.
To me, the latest version is definitely worth the cost of the upgrade. However, getting the existing sets that you have (if they are the annodized sets) upgraded to the latest firmware version will not be expensive and might serve you well enough. You should discuss these issues with your instructor. Qualified Optima instructors understand the history and issues, and should be able to suggest viable options for you.
Enjoy your Optima.
