Smaller, holds more measurements, takes different measurements, ease of transferability of data.
Interestingly there are a lot of parallels to that article and wildlife telemetry and tracking tags. One of the things I'm getting into in my own research program is tagging individual fish and following their movements in space as well as their thermal (temperature) behavior and depth patterns. One thing is clear in the past ten years, tagging devices have gone from the kinds of things that could be used only on dolphin sized animals to now having the ability to tag larger bluegill sunfish.
Interesting reading and thanks for the post!