« on: December 03, 2013, 11:02:23 AM »
The smaller size of the 500 II would make it easier to travel with, especially by air. As you say, the most significant differences are the cost and the 100mm of focal length. I'd say the 500mm would be better for wildlife and birds, whereas the 600mm is better for birds and wildlife. Since the latter more closely matches my interest, I went with the 600 II.
I had an elementary school teacher who when teaching set theory tried to tell me that 3 x7=21 was not the same as 7 x 3 = 21, some how the order of the number of sets and number in the sets was important to determining that there were 21 total items.
Both are great lenses. Personally I went with 500mm for the lighter weight, even though my interest is birds and wildlife.