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

[ahab1372]

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.