@Ant1: I'm glad you like my pictures
To be honest, I'm not much of an expert concerning macro photography. My gear consist of the 35mm, the 50mm, the 70-300mm and the EX-25, but for some reason I always feel that I have the wrong combination of equipment with for the things I want to do.
I usually use the 70-300 because it can deliver a maximum aspect ratio of 1:2 just like the 50mm, but also works as a tele lense, meaning you can use 1 lens for 2 purposes (and I don't want to carry too much stuff with me). The 50mm on the other hand can be a great lens for portrait photography, but the AF is rather bad - it will fail you even in normal indoor situation with windows. It's rather embarrasing. With the 35mm you get an aspect ratio of 1:1, but you need to get so close to your subject that lighting seems to become a problem.
So, why do I prefer the 70-300 for insect photography?
Insects often move fast between one flower and another. While people with more patience might wait for the perfect situation and use a tripod and manual focus, I don't, so I need
a) Autofocus, which you don't get with the EX-25
b) a larger range of distances from the subject your lens can handle. With both the 35mm and the 50mm you have to get rather close to the insect, meaning you have to follow it from flower to flower. With the 70-300mm you can keep your distance and just follow the subject with your camera. You might not get the best aspect ration, but with so many megapixels at hand, cropping is no issue (at least not for me)
c) did I already mention you need lot's of light? Too bad for the 35mm
I haven't tried the 35mm with the EX-25 yet (I received the lens last week and there are no insects around at the moment), but I don't think it would work. Still, 1:1 aspect ratio on 4/3 is pretty neat, see below.
Some comparison shots for the 50mm, first without and second with the EX-25: