Wouldn't a 150 macro work out to an equivalent of 300mm on a 4/3rds camera? That's very, very long.
Maybe; that is why both the 105 and 150 are on my short list.
However, at macro distances, the relationship between focal length and image coverage gets a bit complicated, so that in effect 150mm in 4/3 is like about 200-225mm in 35mm for 1:1 macro work, as far as working distance when filling the frame with the same subject.
Example: to fill the 35mm frame with a subject 36mm wide, you use 1:1 magnification, m=1, while with a 4/3" sensor, you want an image half as large, 1:2 magnification, m=1/2. The working distance (subject to front of lens) is
working distance = (focal length)*(1+1/m),
so
working distance = 3*(focal length) for 1:2 (m=1/2)
working distance = 2*(focal length) for 1:1 (m=1)
working distance = 1.5*(focal length) for 2:1 (m=2)
In that situation of "1:1 equivalent", the "35mm equivalent focal length for equal working distance and field size" is only a factor 3/2 greater:
- the 150mm in 4/3 format gives working distance of 450mm, the same as with f=225mm in 35mm format
- the 105mm in 4/3 format gives working distance of 325mm, the same as with f=163mm in 35mm format
With even smaller subjects, needing 1:1 in 4/3" format, 2:1 in 35mm format, the ratio is down to 4/3, so
- 105mm with 4/3" like 140mm with 35mm
- 150mm with 4/3" like 200mm with 35mm
Since 180mm and 200mm are popular in high end macro lenses for 35mm format, those equivalents are not out of line.
I have done near macro work with my 50-200 at 200mm, and a bean-bag for low level stabilization.
And for non-macro work, a reasonably bright (if slow focusing!) 300mm equivalent is attractive. My nature photography often jumps between "small" and "distant" subjects.