Rent, trust me. Snowboarding looks like the coolest thing in the world but there is a lot of headache involved that if you don't get the riding thing right away, will ruin your boarding experience. That being said I have been riding a snowboard for close to 8 years now and while I am not X games good I can confidently ride down a black diamond trail at Lake Tahoe (which I did last winter). So I will share some of my impressions and feel free to take them with a grain of salt.
Reasons why you may want to rent and not by:
The bindings, which can cost more than the board, are very important. If you are not used to them, they can really hurt your feet and ankles. You want them tight but still allowing for circulation. This takes a while to dial in on bindings you are not used to and even longer if you are not used to how bindings should fit. It might feel great in the warming house, but after 2 minutes of riding you might be in a lot of pain. It will be a lot of trial and error that first day and you may not want to deal with it the rest of the time.
Getting off the lift will be embarrassing because you ride up with only one foot in the binding and it takes a lot of practice to smoothly ride off the lift without crashing into the others getting off. Get ready to do that a lot.
To go anywhere on the mountain with out surfing down hill requires a awkward twisting of the downhill leg and kicking scooter style with your free leg. This can become very tiring but your only other option is to unbind and walk, then re-bind which is a hassle.
Carrying your board on a plane will cost you money because it is considered over-sized luggage. And unless you don't care if your board arrives in working condition or having the binding stolen off it, you'll need to buy a travel case which will sent you back more than a few days rental costs.
You can learn the riding basics (turning , riding, and stopping) from a friend who knows or an instructor and in just a few hours and be happily sailing down the mountain. If you learn on your own, it will eventually happen but it will be a painful experience.
Even the most athletic of people with great balance can take some practice before they make it down even the bunny hill. There is some patience required while you get the feel for it.
It takes more energy than you think, so just be prepared. Boarders ride the edge of the board so stamina will be a factor because of all the leg muscle you will be using.
In the beginning spills can happen suddenly and without warning until you get used to how far over on a edge you can ride. My second day of riding I knocked myself uncontentious when the toes of my boots dug into the snow like a emergency brake at the top of a hill. I then flipped over backwards and downhill hitting my head on a ice frozen downhill. I woke up to a random skier asking me if I was ok.
All this being said snow boarding is the best. The best analogy I have for it is skiing can be compared to driving a sports car, but snowboards is like riding a sport bike. Once you get in a groove and start to make it down the hill without wiping its the best feeling. You feel like you are flying down the hill. And its nice that everyone will think you are cool.
