Keep or Sell 24-105 f4 for 24-70 f4

I have had the opportunity to use both lenses. For most photographers, the 24-105 is going to be the better choice on the basis of flexibility and functionality. While no lens has "perfect" image quality - and the 24-105 has its issues - it can produce excellent results. The IS feature can be very useful for hand held shooting in may cases, and the added focal length at the long end will be appreciated by most shooter.

The image quality issues with this lens pretty much turn out to not be real issues at all for most shooters. It exhibits some noticeable barrel distortion at 24mm and vignetting at f/4 at the wide end. However, typical conversion software automatically compensates for these issues very effectively.

The 24-70 f/2.8 is a fine lens. While the IQ from the 24-105 is very good, the 24-70 is somewhat better, especially in the corners at larger apertures. The f/2.8 aperture can provide a small advantage in a few cases with a bit more background blur ("bokeh") and one stop (only!) of shutter speed in low light. However, at a cost of well over $2000, this is not a lens that makes sense for most shooters, who probably won't see any real improvement in the quality of the photographs they share.