Why are my limited lens selections even in play with this topic?
We are talking about wielding a 300mm f/2.8 (5-lb) monster versus a 120-300mm f/2.8 (5-lb) zoom telephoto of significantly good quality. Anticipation would say that having a great zoom would be the preferred way to go with just the flexibility aspect, alone.

You have:
  1. your prized f/2.8 aperture
  2. a relatively decent MTF chart
  3. the newest in lens stabilization methodology
  4. a massive 105mm first element

Good lord, just cast off that Nikon anchor of yours and step up to flexible photography. What I have and done has nothing to do with that. This is for YOUR benefit and anyone else who is hauling around a Nikon, Canon or Sigma DSLR camera body. I have no real stake in it, other than seeing your photography grow and get better. Heck, just think of all the wonderful and brilliant shots you could achieve by being able to slip that zoom wider and frame to and fro... turning out outstanding images. You could even probably recover the $2600 you are currently wasting with a fixed lens. Pick up a NEX7 with it... the adapter for Nikon and have at it.

Never mind my optical solution path. We are talking about YOURS!