Are you sure the site you saw was talking about the ATI 7500 Radeon mobile chipset? There are a couple of models that fall under the name Radeon and the 7500 is the new one. On the sites I've seen about the Radeon 7500 they found that the ATI 7500 mobility Radion was faster.
http://www.inqst.com/articles/radeon/0826main.htm
At the address below someone posted that their Dell laptop equipped with the ATI 7500 mobility Radeon scored 3617 on 3DMark 2100
http://www.pcgamereview.com/reviews/video_cards/product_1589.asp
Maximum PC gave the Dell Inspiron 8100 laptop with the ATI Mobility 7500 its the "Maximum PC kickass product" award when they reviewed it in the Jan 2002 issue
"...the Mobility Radeon 7500 stands as the fastest graphics chip available at press time-at least until nVidia answers with it's upcoming NV17M chipset."
In the review ATI 7500 achieved an average 123 fps in Quake III
"For notebooks, we use a different Quake III test. Instead of our own homegrown demo (which we feel is too demanding for notebooks), we run the very popular Demo 001 at 800x600, 16-bit color, at normal detail settings. We report the average frame rate; higher scores are better"
~details on benchmarking tests from the Maximum PC site
After the Geforce 4 go (NV17M) is reviewed and tested it the top mobile graphics chips will probably rank something like this.
#1 Geforce Go Mobile
#2 ATI 7500 Mobility Radeon
#3 Geforce Go Mobile
I've looked around online and while the Geforce 4 Go is available from Toshiba in one of it's laptops, it only has 32 MB of RAM while Dell offers the ATI 7500 mobility as it's top Graphics chip with 64 MB of RAM. I'm waiting to for a head to head review between the 7500 mobility and the Geforce 4 Go both equipped with 64 megs.
The ATI Rage M4 will get it's ass kicked by the Geforce 2 go. It's not ATI's top mobile graphics chip though.