If you only dive once a year its probably best to rent gear on your vacation. However if you want to enjoy it more often its probably best to get your own equipment. I'm very nervous of renting life support equipment in an unknown location. I much prefer having my own equipment - I know it's been used properly and well serviced. My whole family has their own equipment.
BE WARNED - Whenever you walk past the closet where your dive gear is stored, it will call to you
"Psssst - Lets go Diving"
Diving equipment is like anything else - there is a huge price range. Rodales web site does equipment reviews and this can be useful as a guide to equipment choices. Obviously, the more you dive, the better value having your own equipment becomes. Also with your own equipment you know where all the releases and controls are, which makes you more comfortable underwater.
Personal equipment (Mask, Fins, Snorkel & Boots) costs about $250-$300. An open water training class costs about $300. They forget to tell you that you need more equipment as you do more classes. For example, for need lights for the advanced open water night dive.