1. Build quality of 70-200 L lens is outstanding from what I've read.
2. 70-300 f/4-5.6 has a focus ring that rotates during AF which can cause issues if you have a hand on it when it's focusing. I could see that being an issue.
3. 70-300 f/4-5.6 has a front rotating element which makes using polarizers next to impossible.
4. photozone.de results for 70-200 are amazing. According to those tests the lens is excellent throughout it's range and across the entire image
5. I figured you only live once and I was fortunate enough to have the mondy to get it so why not.
It will be here on January 20th. I'm excited to try it out.