I've had one for a few years. They are not very durable but mine is still working. I think the basic one is all you need. I agree get the whiffle ball brand and don't use when the balls get wet.
I have heard of good results with a different brand that uses a blower kind of power that reportedly works more consistently and damp balls would not matter. That's good if you are in high humidity areas and want to practice in the morning while it's cool.