Olympus 75-300 Mk1 vs. Olympus FT 70-300

The 75-300 M. Zuiko does very well at the long end. I pretty much have always treated the 300mm end of the four-thirds 70-300 as an f8 lens. It's just never seems to do all that well unless stopped down. The 300mm end of the M. Zuiko is already "stopped down" when wide open at f6.7 and is plenty sharp for me at that focal length.

The main differences between the two favor the micro model (size and much faster focus speed) in two, and the four-thirds model (close focus distance) in one. The Micro model is way smaller in physical size and weight compared to the four-thirds 70-300. After hauling the 50-200 f2.8-3.5 around the 70-300 f4-5.6 seems pretty darn light but the micro model takes lightness in a tele zoom to a new level, and af speed-wise, it's no contest with the micro model focusing much, much faster and silently compared to the wheezing you can hear with the 70-300, especially if it happens to go through one of those full-range dry heaves it can go through.

In terms of focusing close the four-thirds 70-300 takes the prize going away. The Micro model can focus down to 2.96 feet, but only at 75mm. From 76-300mm the closest focus distance is closer to 5 feet so you need to use closeup attachments or the Kenko auto extension tubes to do any type of close focus work, OR, you can use the digital 2x TC which will not get you physically closer but doubling the magnification makes the subject bigger in the frame.

--
"There's shadows in life, baby.." Jack Horner- Boogie Nights