I would say propane is probably more popular. Electric is used a lot in food warehouses and freezers. I would personally rather have a propane one. Using only 4 times a year or so you might want to get in the habit of starting it and running it a little every few weeks. I would also have a spare propane tank on hand for when someone runs out of fuel (they will.)
If you get electric and the battery dies on you, you're screwed. You're going to push it back to the battery charger and be waiting hours for it to charge.
When buying one other than checking general things (fluid levels, how it runs, etc) I would raise the forks, preferably with some weight on them, and see if the cylinders leak down. At the very least look for any hydraulic fluid coming out of the lift cylinders. I'd probably take a pallet with me that had a few hundred pounds on it at least and use that as a test and also to make sure it could lift it with ease.
Also, I'd look to see if there is someone close who can service forklifts. Find out the brands they service and narrow it down to that. You don't want to get a forklift that no one around you can work on. Some very common brands are Yale, Hyster, Nissan, Toyota, Clarke, you probably won't go wrong with those.
