One of the biggest advantages of having my Olympus micro four thirds system is the ability to conveniently have a lens with a lot of reach with me at all times even when I am not out seeking wildlife images. This is an example of that taken during a salvage yard shoot. It was taken with a 2x teleconverter for a full frame equivalent of 1,200 mm. If I had a larger full frame system, I would probably never bring a lens with this kind of reach along unless the main purpose of the outing was to get bird photos. A 600mm f4 is just too big and heavy to carry around all the time "just in case".