Computers are another HUGE consideration when diving.
Are they needed?
Most dive boats require them on all dives. IF you don’t own one, they will usually have them available to rent.
But why not own your own? It is one of the pieces of equipment you rely to keep you safe, literally keep you alive, so maybe you should own one so you have the peace of mind that it is in perfect working order and you are accustomed to using it.
Features and price come with experience. Start simple and move up when your needs and dive level necessitate it.
Computers have batteries, batteries can fail or the computer fail from flooding unexpectedly. Tech divers usually have a “Backup” analog gauge just in case, consider that.