Option 2: Canon EF 500mm f/4L IS II USM Lens
- Excellent optics
- Less versatile prime lens
- Shorter focal length with same max aperture as the 600
If you have the money to spend, it would be difficult to argue any lens about the new Canon 200-400 w/ TC for wildlife photography unless you fall into a specific niche of wildlife photography where you'd need something specific. It's absolutely awesome. In fact, this lens is so good that I know some wildlife photographers who switched over to Canon just so they could use this lens.