A previous item pointed out how eValid could pretend to be a particular smartphone, and looked at how several different websites behaved in delivering material to that smartphone client browser.
A companion experiment that we did tried out five different smartphones on the Amazon website. (We chose Amazon because it seemed to be one that had very good smartphone options.) The results are shown in Mobile Agent Test Page -- Multiple Phones.
What is interesting about these data points is how much the size of the download varies from phone to phone: a ratio of 6.15+ from largest to smallest download volume.
If you are concerned with optimization of an application to a range of different smartphones this comparison method will be of great interest.