This is a timely thread for me and is giving me important information when comparing the 24-70 v 24-120.
I have the 24-70mm which is perhaps my favourite lens and never considered giving it up, however I have been wondering for a while whether due to weight and no VR if the 24-120mm would be more practical. This in terms of both weight and flexibility.
I have some experience of this decision making between two lenses when I decided after much deliberation to change my 14-24mm for the 16-35mm f4. Weight was not a factor, but I wanted to use filters and anyway I often found the 14mm end too wide on FX. Once changed I have never missed my 14-24mm and find it far more flexible now I have a longer reach and can use filters.
This thread has now made me think seriously about swopping the 24-70 for the 24-120 f4. To be honest I am not a photographer who really pixel peeps or prints massive sizes, so am unlikely to be disadvantaged by the change.