You would think so, but I found some interesting results when doing the "everyday use" tests. The Beige G3 (333MHz G3, 768MB RAM) was significantly slower in running Mac OS X Jaguar than the iMac G3 (266MHz G3, 192MB RAM).
If it was a Blue & White G3, it would probably be a different case once again, with the B&W smoking the equivalent series iMac G3.
If you're all for giving it the Mac Modders' Touch though, the Beige G3 would be quite a screamer. Upgrade to a faster G3 or G4 ZIF, max out the RAM, give it a decent sized hard disk or two, a PCI graphics card, USB card, FireWire PCI card and perhaps even bump up the Frontside Bus clock speed (quite easy to do on these machines).
Unfortunately with a Beige G3 you'll still live with the issues of an Old World ROM. XPostFacto wlll get you up to Tiger on it, and even Leopard if it has a G4 ZIF and you have access to the Leopard Developer Preview "Gossamer KEXTs", but there can be quirks with getting XPostFacto to do its thing in the first place, as I found.