Those lenses are both spankers, and to be honest one of the main reasons why micro four thirds is still in my life, I love my two. You might have some trouble deciding which one to get, as the 40-150 is a brillant general purpose telephoto zoom, for kids, pets, portraits, large wild life shooting (i've even shot garden birds on it without the converter). The 300mm F4 is just sublime, Tack sharp from wide open a great 600mm effective, plays quite nicely with the converter for an 840mm F5.6, and yet reamins compact, reasonbly light (for what it is) and very portable. Also the IS on it is amazing with an Olympus body for dual IS. About the only critisim I coudl level at the lens, is that you might need to watch your backgrounds, as under some circumstances (with lots of trees or branches just behind the subject), the bokeh can get a bit nervous (but not objectional to my eye).