I took a drive over to the golf course late yesterday afternoon, right at sundown with both the 55-300 and the A*300. I really do not do that much telephoto - especially handheld, so this was a wonderful reminder - of how pi** poor I'm at telephoto and hand holding long lenses.
My take - for me, need a much faster shutter, which pushes the ISO up, so that you can have a decent range of aperture from which to select. I need a faster shutter to help the image stabilization. Technique, skill, practice, with a dose of talent is necessary to get a good shape image - mine were not that sharp due to some "motion", and I really needed to push up the ISO even more to gain a faster shutter.
The AF on the DA 55-300, was a godsend. The MF on the A* made me appreciate the AF even more. The weight difference between the two - had me respond differently to each - technique, technique - followed by practice and practice - with a lot of skill thrown in (skill is not necessarily me).
Back at the house, I did like the images from the A* better in terms of color and rendering - by a smudge.
So, to do this all over again, I would want the A* 300/f4 with AF, which results in the DA 300/f4. Bottom line is there is a $1,000 difference when compared to the 55-300 using new prices. Using used - its double the price of either lens.