I am currently evaluating if I should upgrade my EOS 550D with a really nice 6D. The main reasons for this are:
- bigger body, but still not as big as the 550D with the battery kit mounted, thus it's better in hand
- bigger viewfinder
- MUCH better low light performance (probably the main reason)
- full frame sensor (a little bit more detail)
The main use of the camera is everyday pictures. I always carry my 550D with a Sigma 18-125 lens with me around and I like the range of this lens. I picture mostly animals, landscapes and buildings, but normally no people.
I compared the two lenses over at Dxomark, here the compare with the 5D MK2: http://www.dxomark.com/index.php/Lenses/Compare-Camera-Lenses/Compare-lenses/(lens1)/211/(brand)/Tamron/(camera1)/483/(lens2)/164/(brand2)/Canon/(camera2)/483
The canon is a bit sharper, but with "only" 1/3 of reach. I don't think I'll feel the difference of 24mm to 28mm at all with my shooting habits.
What do you think, should I take the better and sharper Canon lens, but loose quite a bit reach, or is the difference in sharpness anyway not visible if I'm not going to pixel peep?