It's a tradeoff of speed versus cost.
If you want as fast as possible to your hotel, arrange for a private driver. As soon as you leave the terminal and spot him, you're off to the garage to get the car and you're off.
With Interbus, it's about half the price as the private driver, but you will have to wait for the van to come pick you up after the guy with the clipboard calls them. It's usually anywhere from 5-15 minutes, but I have waited over 30 minutes a couple of times when the bus was stuck in "traffic" on the way to the airport. Funny thing is that on the way into town, the traffic to the airport magically disappeared. And a couple of times I had to wait for other passangers on my flight. So we wait 10-15 minutes and they usually don't show anyway.
The other thing is that it's only a decision you need to make when you're arriving alone. if you have anybody with you, it's a no-brainer; private driver. Interbus charges per passanger whereas private driver charges per trip (no matter how many people).
Plus, for a newbie, an English-speaking driver who can give you some tips/advice on girls, safety, etc is a big plus IMO.