My pockets are not as deep as I'd like, so I only have the Oly 60 and the Panasonic 30 to use for my macro, but it's the difference between the two lenses that is often the deciding factor on which aperture I'll use, despite both lenses being f2.8's.
The Panasonic is quicker to focus and it's my first choice for insects flitting from flower to flower - for stuff that's on the 'go', including moving beetles, spiders and so on.
I also prefer it in low light and it's the lens I'll stick on the camera when on walkabout as it gives me a far better chance of getting a photo of anything I see before it flies or runs away. I'll typically have the camera in manual, with ISO on auto, a slowish shutter speed of about 1000 and 5.6 dialled in for aperture. These settings can be changed as the situation develops but it's a good base for me and the light I have here in SW France. With mechanical shutter and in burst mode, it's noticeably more nimble than the Oly 60 for responsiveness. And despite the seemingly huge problem for many people of its short focal length, it can be surprisingly effective at close quarters.
The Oly is great for situations where the quarry is settled and not moving, and where I'll mount a flash and perhaps an achromat. It's a lens to be used at a measured pace. It can be used for flying insects, but that has to happen where the action is repetitive and easily anticipated, such as a particular flower that is producing pollen constantly and you'll notice a pattern to the visitors. With its longer minimum FD the Oly is also great for shy insects (even that extra 8.8cms of distance can mean something sometimes), and at 1:1 it's the obvious choice. As the Panasonic does not do anything with achromats the Oly is also the choice if I want extra magnification.
All of this can be done with apertures ranging all the way up to f22 if needed, though typically I'll be dialled in to something between f9 and f13 or so - it all depends on the light as m4/3's loses its integrity when you start playing down that low. I find clean files are hard to come by in low light and close magnification, on my GX8. Handheld focus stacking will be a major consideration if I can ever afford to upgrade.
Both lenses are fairly equal in image quality. I never choose one or the other on that premise, anyway. And if I am shooting indoors, for something other than insects, or an insect in situ, then all of the above can be rearranged to suit. I hasten to add that I've only been shooting insects for a few years, and I am certainly not an expert, but I enjoy shooting stuff that moves - it's challenging and sometimes rewarding. The emphasis on 'sometimes' is important, though!
