We don't really have much of a preference when it comes to which reader you use with ClearStream. We have found most of the readers to be very stable when running with ClearStream. Some of the readers have some additional features that are accessible within CleartStream. For example, Motorola/Zebra readers have a tag reporting section on the Reader List form that allow you to control when and how tags are reported to ClearStream at a hardware level. This will also allow you to receive a tag event when a tag has left the range of the antenna.
So, it's really up to the user what their preference is.