17-55 ef-s + 24-105, or 24-70 2.8?

Looking for opinions- Currently have a 7D with the 17-55 2.8 EF-S lens, which I love. Didn't think I'd upgrade to full frame anytime soon, but the 6D is looking good, particularly for its low-light capabilities. I shoot mainly low light situations like concerts. So 2.8 is really about the slowest I can use for a lot of shows.
It seems a no-brainer to get the 6D bundled with the 24-105. Trying to decide if I should keep both lenses, and carry two bodies at shows, with fast primes on the 6D and the 17-55 on the 7D. OR sell both and buy the 24-70 2.8 (original). I think the 2.8 might be more important than IS. Anyone of experience with all these lenses?
Thanks!

there have been similar threads here about this question. The overall answer is that the 6D with the 24-105 will still give you better IQ in low light than the 7D with the 17-55 because the larger sensor more than compensates for the one stop you loose in max aperture, so there is no reason to keep the 7D/17-55mm combo for low light.
2.8 on FF will of course be even better for low light, and fast primes even better than that.

6D with an f/4 lens will beat a 7D with an f/2.8 lens for low-light performance.

OK, thanks guys! Just needed a little positive reinforcement to make me feel better about spending the dough...

Experience with all of them yes.

This would be my suggestion.

Buy the 6D, if you want to get the 24-105 package cheap do it, then sell the 24-105. I have seen them going for about $825.
Sell your 7D and your 17-55mm. Take all that money and buy the 24-70mm f/2.8 II. After a month with this kit you will never doubt your decision.

F/2.8 on a crop body has a much wider DOF. You will notice the increased performance and abilities you will have with the full frame camera over the 7d. Keeping the 17-55mm because it can go to f/2.8 on a crop body when you own a FF, doesn't make sense.

There are a few reasons to keep the 7D if you go full frame 6D. The reasons would be back up body and if you need a sports camera with the illusion of extra reach.

As a backup body it will probably collect dust once you get the 6D and the 24-70mm II.

Stay away from the 24-70mm original, there are better lenses.

6D with 24-105 is currently $2,399.00 on B&H when you add it to your cart.

Ryther Camera has the 5D MK III for $2,199.00, you could just about get a f1.8 50mm, add some tax and walk away for the same amount. That's grey market though. I wonder if maybe they'll be in stock depending on how many high markup accessories you insinuate you would be purchasing, at least I read that this is the scenario in some grey market stores who profit little to nothing on the grey market items. Couldn't hurt to have grey market because you'll insure it anyway. I read somewhere that Canon will service it if you show a purchase slip regardless. Put Magic Lantern on it, what could go wrong?

@HDNitehawk- Thanks for the advice. Seriously considering getting the 24-105 and selling it along with the 17-55. Plan on keeping my 7D, both to have a backup body, and for the extra reach for wildlife and other far-away shots. Or would a cropped full-frame shot at 300mm still be better than a 7D/300mm shot?

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Originally Posted by gbc

Plan on keeping my 7D, both to have a backup body, and for the extra reach for wildlife and other far-away shots. Or would a cropped full-frame shot at 300mm still be better than a 7D/300mm shot?

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A 6D shot cropped to the APS-C FoV will have equivalent IQ to the upcropped 7D at low ISO (less that ~800), and better IQ at higher ISOs. So, assuming 7.8 MP is enough (prints up to 16x24"), there's no advantage to the 7D from an IQ standpoint.

However, the AF of the 7D is better for moving subjects. If you were getting a 5DIII, I'd say the only use for the 7D would be as a backup (I'm not even sure I'll keep my 7D, after getting the 1D X I haven't even used it for anything but some test shots). But with the 6D, the 7D is going to be better for moving subjects, and I think better AF will trump IQ in that scenario, at least up to about ISO 3200 - above that, the 7D IQ is not really usable, IMO, and if the 6D's AF can't keep up you'll have hit the limit which only the 5DIII or 1D X would let you overcome.

Quote:

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Originally Posted by gbc

@HDNitehawk- Thanks for the advice. Seriously considering getting the 24-105 and selling it along with the 17-55. Plan on keeping my 7D, both to have a backup body, and for the extra reach for wildlife and other far-away shots. Or would a cropped full-frame shot at 300mm still be better than a 7D/300mm shot?

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It is the AF on the 7D for action shots that you will miss the most. You say wildlife, if you are talking stationary deer or sitting birds you would not miss the 7D as much with the 6D when you crop. If you are talking birds in flight then the 7D would be the choice to keep. Neuro's description is accurate of what to expect with the IQ on the long end.

My philosophy is this, I would rather have the best of the best that I can afford for my favorite type of photography. Make do with that gear for the rest. I would give up the back up or a bit of reach to have the best gear for my favorite type of shooting.