Canon EF 28-70II vs 28-105 II

I have a 28-105 II USM EF I use as a walkaround lens. Anyone have hands on experience using both of these two lenses? Image quality equal? Significant physical size/weight difference? Any other things to consider? Or, an alternate 3rd party that is comparable? Appreciate your input.

I only have the EF 28-105mm f/3.5-4.5 USM and I'm very happy with it.
Performs quite well IMO and the extra reach is very useful to me when I want/need to travel light (camera and one lens). It probably has its optical downsides over the 28-70mm, but the 28-105 has USM which I also appreciate.

Also, see this exact question answered here.

Buzz-01
I have the 28-105II. I am wondering if there is any size advantage with the 28-70II for walkaround use. I should have stated that in the original post.

Ah I see. According to this comparison, the difference in size is not that much.

^^ I'm surprised. I thought there would be more size difference. I'm satisfied with the 28-105 image wise, so I will stick with it. Thanks for your input.