I have been considering buying a 7dii as an upgrade to my 40d. However, I have read a bit about the 6d and how it is a great low light camera, which is my biggest desire as far as upgrading goes. There's nothing wrong with my 40d, but I would like higher ISO options since I will be taking a lot of photos indoors and I don't like to use flash for candid photos. I mostly take photos of people, and my main concern for upgrading is that I want to be able to take good, sharp photos of a baby and small children inside when there's often not the best lighting. I also love random macro with my 100L. Right now, I can get the 6d on sale for less than the 7dii.
However, I do sometimes take action photos (sports--kids and adult fun leagues; birds and wildlife outdoors). I'm hoping anyone who has used a 6d can comment on its ability to perform for action photography when it needs to, because I've read only the center point is very good for this. I don't do a lot of action photography where I'm actually using Servo and high speed burst, but I do occasionally and don't want to buy a camera that will not allow me keepers in those situations. I did recently purchase a Sigma 150-600c for birds, etc. and although I don't go out for that specifically very often, I don't want to "waste" that lens. If you've used it for action, do you get good results if you use the centre point? I'm assuming cropping afterwards if needed would be okay for me, since I'd be moving from a 10mp 40d up to 20mp the quality will probably still be what I'm used to.
Also, are there any other issues I should be concerned about with choosing the 6d over something like the 7dii? This is a big decision, and I will have to sell either my 17-55 2.8 if I buy the 6d or my Tamron 28-75 2.8 if I stick with a crop camera. (Planned on selling one or the other anyway, but I'm nervous about going back to using the Tamron after using a 17-55 for 2 years!)
Any advice would be appreciated.






