You've seen my voice recorder. What you want to look for is easy of operation, size small enough to be covert, but large enough you can operate the device without removing it from your pocket by touch alone.
My next recorder is likely to be a plastic card name badge like you'd get working for a large corporation. They are about the size of a driver's license or slightly larger. They are typically worn on a clip attached to your shirt or jacket. One covert type has a video camera built right into the name badge. So when they look at your picture on the name badge, they put their face right smack in the middle of your evidence. And they done it of their own volition! Can anybody say "Gotcha!"?
Another cool device is a recorder that takes video and audio, and otherwise appears to be a normal wrist watch! How cool is that!?!?!
Another cool gadget is a pair of sunglasses with video camera and audio built right in!
When I am recording an interaction or encounter, I prefer that my device be covert and known only to me that it is operating. However, that being said, any recorder that gets the voices down clearly is better than no recorder at all. Check out Best Buy. They have a variety of recording devices you might like.