Hi Luis, I currently have the 12-24mm F2.8 and I think it is a really fantastic lens with sharpness throughout the range. At the 12mm length you're able to capture more in your image without having a major curved distortion if you are taken a photo a horizontal level and not aiming upwards or downwards.
In retrospect I wish I would have gotten the 16-35mm because of the extra zoom range near the 35 for composition reasons.
On my 24-70mm I often find myself zooming towards 30mm range for composition. Personally for my situation, I think a 16-35mm would be a nice replacement for a 12-24mm and 24-70mm
