Wow, a second-hand 500 II is cheaper than a brand new 600 III, thanks for that I'd have never have thought that possible. let's stick to valid comparisons. You act like people in this area of the market are scratching to make a living. If you are really breaking the bank to get one of these you really should look at other alternatives. The price differential of the 600II and 500II had little effect on people's purchases, it was size, weight and reach. Size is still an issue for the 600III, weight is no longer an issue and for travel in a lot of planes, it's only the weight that matters. You can get light bags that'll carry the 600mm lenses. Also, if size is an issue get the 400 III and sue the 1.4x TC III, gives you a 560 f/4 much shorter than the 500 II. The 600II is very popular for pixel challenged cameras like the 1DX and 1DXII and a more popular choice. 600III would be even more popular now. Alas, Canon don't make a high MP 1 series to make the 500II more viable. I got the 500II because I had the 1D4 and then 5D4/5DsR to make up for the loss of reach but none of them have the AF of the 1DXII.