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

[gbc]

OK, finally got the 5DMIII. Now looking for the general purpose lens. As mentioned before, was using the 17-55 2.8 on the 7d. Considering the 24-105 now. I've read on a few forums that the f4 on the 5DMIII will be better or just as good in low light as the f2.8 on the crop sensor. Is this true? I'm pretty happy with the low light performance I've been getting with the 17-55/7D combo, so if I can get something close to that with the 24-100 without having to splurge for the 24-70 II (or the Tamron 24-70), I'd be satisfied with that.
Though I WILL be selling the 7D and 17-55...

[Busted Knuckles]

OK, finally got the 5DMIII. Now looking for the general purpose lens. As mentioned before, was using the 17-55 2.8 on the 7d. Considering the 24-105 now. I've read on a few forums that the f4 on the 5DMIII will be better or just as good in low light as the f2.8 on the crop sensor. Is this true? I'm pretty happy with the low light performance I've been getting with the 17-55/7D combo, so if I can get something close to that with the 24-100 without having to splurge for the 24-70 II (or the Tamron 24-70), I'd be satisfied with that.
Though I WILL be selling the 7D and 17-55...

I have the 24-105 on the 5dIII and am generally pleased... but.... I picked up the 40 2.8 pancake and it really points out how soft the corners of the 24-105 actually are.

I am toying with the idea of the 24-70 2.8 or perhaps going to primes - w/ the low light performance of the 5dIII it is an interesting question.

[HDNitehawk]

I've read on a few forums that the f4 on the 5DMIII will be better or just as good in low light as the f2.8 on the crop sensor. Is this true? I'm pretty happy with the low light performance I've been getting with the 17-55/7D combo, so if I can get something close to that with the 24-100 without having to splurge for the 24-70 II (or the Tamron 24-70), I'd be satisfied with that.

Yes, close and it is your cheapest option.

Your best IQ will be from the L primes, if you know what length and only need one length it would be a cheaper option than the 24-70mm f/2.8 II. I was never happy with the IQ out of either the 24-105 or the 24-70 I so for years I covered the range with several primes. I now own the 24-70 F/2.8 L II and use it as my carry around lens. I still favor the L primes when I have specific tasks.