Quote Originally Posted by HDNitehawk View Post
Other than being able to shoot at 300mm at f/2.8, it will be a tall order for the 120-300mm to compete in IQ. The 300mm f/2.8 I and II version are both in a league of their own. The 70-200mm F/2.8L II doesn't even compete in this league.
Definitely the L IS and L IS II will both be better than the Siggy Zoom.

But they'll also be what? 2x, 3x, 5x the price? If you need the best, of course you're going to choose L. But if you need the best for what you can afford, I don't see the L being 2-5x better. That's where companies like Sigma operate, not the best, but the cheapest past the point of 'good enough'.