500 x $10K or 600 x$13K

[dolina]

While canvassing for a 600 II I found out that Canada has a tax rebate scheme. If you you are visiting canada you can avail of this.

http://www.photoprice.ca/product/03580/Canon-EF-600mm-f4L-IS-II-USM-price.html

http://www.visitorstocanada.com/visitortaxrefund.html

Without tax a 600 II sells for CA$11,395.44 vs BH's $12,800.00.

[natureshots]

So, when you do get round to doing your testing, make sure you compare both with a 1.4TC and crop the 1Dx, you might be surprised.

Probably not.  The reason I haven't been terribly motivated to set up the test is that I've done the test between the 7D and cropped 5DII (about 18 months ago, now), so I know the only difference is MP not IQ, and the 1D X is better than the 5DII for sensor IQ.  I assume the test with the 600 + 1.4x on both bodies would show the same, or an advantage to the 1D X at higher ISO. That test is less relevant now that the 1D X supports f/8 AF - not much difference in pixel-level magnification comparing 2x on FF to 1.4x on 1.6x crop.  I disagree with natureshots that the 7D + 1.4x will optically outperform the 1D X + 2x.  That might be true with a lesser lens, but the MkII supertele lenses just don't take that big an IQ hit from a TC, even a 2x (and keep in mind that the 600 II + 1.4xIII beats the 800/5.6 for IQ).  As for AF, while the 7D's 19-points are very good, the center point of the 1D X is better.  But the real kicker is that most times I've been out shooting with the 600 II, my ISO has ranged from 1600 to 6400. The bottom of that range is ok on the 7D, but the top end just doesn't cut it on the 7D. 

For those reasons, I'm pretty sure the 7D gives me no advantage over the 1D X, other than a few more MP (and not really all that many more, comparing the 1.4x on the 7D to the 2X on the 1D X.

The question I suppose I'm really asking myself is, do I want to keep the 7D as a backup body?  Or should I take what I can get for it, now, and put that money toward a 24-70 II?

So, between 20 and 30 yards, the 7D will work and the FF won't resolve. ... So your test shots depend on what you are photographing and how far away it is.

Would you expect that to be true at, say, ISO 6400?

I am sure that in real world applications the 1dx +2x will virtually always beat the 7D and 1.4x. My real curiosity about the performance of the 7D in bright light really has to do with the rumored 7D II's capabilities as a cheaper alternative to a 1dx for focal length limited applications. Of course you will always get better BIF and low light performance from a FF pro body like a 1dx but my idea is that if the 7D can do well in a situation like a bright field at low ISOs then it stands to reason that the 7D replacement will have better high ISO capabilities and hopefully some decent cross type AF points borrowed from the 1dx then there is great option for bird photographers as opposed to a $6000 camera. I hate spending money on bodies, there value plummets like used cars. By the same token neuro, a 7D will depreciate much less than a 1dx by virtue of the fact that its cheaper. If something happens to the 1dx I'd be psyched to have a backup 7D as opposed to a 600 II with no body. Just my thoughts....

[OCwildlife]

I had the 500f4IS for 3 years and felt it was a good length for wildlife and birds, even for a female. And if you shoot larger animals other than birds, the 600 may be too close much of the time. The added weight is a real issue, unless you are planning on a full time tripod. BTW I bought the new 500 II this month and the weight difference is substancial, enabling me to hike further and hand hold longer. A dream lens.

I added a 2x just for reference and am amazed of the clarity at 1000mm!! My 1.4x could also be used full time, no problems with focusing on BIFs. Clarity excellent with the new lens.

[victorwol]

Well... I finally went for the 600. Thanks for all the comments and help b