The stand-out advantage provided by the PowerShot SX30 IS's 35x optical zoom lens is hard to understate. At the wide-angle end of the range there's little in it with the two cameras delivering virtually identical coverage, but an 840mm telephoto will get you a lot closer to the action than a 600mm, so if you shoot a lot of very distant subjects, this alone will probably be enough to decide you in the PowerShot SX30 IS's favour.
The PowerShot SX30 IS is bigger and heavier than the Lumix FZ100 though and it's battery doesn't last as long, but we did prefer the SX30 IS styling. The layout of the physical controls is cleaner, neater and simpler than the proliferation of switches and buttons on the Lumix FZ100. The simplicity of layout extends to the Canon menu system with its hints and tips system. Much of this is subjective however and, as always, we'd recommend you get your hands on both models before making a buying decision.
Both cameras feature articulatred screens, but the Lumix FZ100's is slightly bigger and wider, while sporting twice as many pixels, factors which make a big difference when shooting 16:9 video. The FZ100 can also shoot 1080i HD video, but the ability to use the PASM exposure modes for filming along with connecting an external microphone are likely to be more of a pull for videophiles. The PowerShot SX30 IS is limited to 720p HD recording and Progam auto exposure mode with Scene detection.
The FZ100's final trump card is the range of high speed burst modes courtesy of its MOS processor. The PowerShot SX30 IS's continuous shooting performance can only be described as mediocre by comparison. And let's not forget the FZ100 can also shoot RAW.
This comparison wouldn't be complete though without mentioning the gap in image quality between the PowerShot SX30 IS and Lumix FZ100. You'll need to look at our outdoor and high ISO comparisons and make your own mind up, but for us the image quality of the PowerShot SX30 IS is demonstrably superior to that of the Lumix FZ100. Couple that with the monstrously long zoom range, and the Canon is hard to resist.