Differences Tamron f/2.8 28-75 / 24-70 I'd like to buy one of those two lenses for filming with a EOS 600D:


Tamron SP AF 28-75mm F/2.8 XR Di LD Aspherical [IF] MACRO
Tamron SP 24-70mm F/2.8 Di VC USD


I am aware of the following differencies of the two lenses.

Advantages 28-75mm:


Some websites claim this lense to be parfocal, which might be interesting for filming.
It's lighter (510g vs 825g)
Slightly lower minimum object distance (33 vs 38cm)
It costs less than half of the 24-70


Advantages 24-70mm:


Vibration compensation (which I always switch off during filming)
USD motor (which doesn't seem to be important for filming)


From that the 28-75 clearly seems to be the better choice. 

Is there anything I am missing? Are there any other points to consider?
Yes, there is a lot you are missing.  

The 24-70 has substantially better transmittance (more light makes it through the lens), slightly better sharpness, significantly less chromatic aberration, 2 more diaphragm blades (better, more round bokeh), full time manual focus (can auto-focus at the start of a shot but still adjust after starting shooting).  

Also, image stabilization can be very helpful when shooting video.  If you are on a tripod you shouldn't, but if you are shooting free-hand, it is a good thing unless you need quick, lag free panning (which would be a problem due to your rolling shutter on a 600d anyway).

While I don't recommend putting too much stock in the overall score that DXoMark produces, there individual discreet stat comparisons are generally reasonably good.  You can find the comparison for these two lenses on the 700D listed here.  (Sadly, they did not have data for the 600D specifically.)