As others have mentioned, there is more to the story than Canon lens vs. Leica lens. I suspect the 6MP sensor is a factor in the FX01's performance. On the same dpreview web site there is a review of the Panasonic FZ7. This camera has the same 6 megapixel sensor as the FX01 and C-Lux 1.
http://www.dpreview.com/reviews/panasonicfz7/
Some quotes from the review:
"Noise is - if anything - worse" (Than the FZ5)
"There seems no doubt that the FZ7's 6MP chip is noisier than the FZ5's"
"noise levels at ISO 80 are higher than the FZ5"
There were very few changes between the FZ5 and the FZ7. The new sensor was perhaps the biggest change.
Others have mentioned color rendition and contrast. I think color rendition and contrast are affected by the sensor and by the firmware as well as the lens.
More contrast in a given scene is not necessarily good. A sensor with a lower dynamic range will create an image with more contrast. I'd rather have the ability to capture a greater range of light and shadow, which takes high dynamic range. It's easy to increase the contrast later on the computer, not so easy to increase detail in shadows and highlights.
To me Canon images over the years have been more bland than Panasonic images. I think of this as more of a philosophical difference that is expressed by tuning the firmware than a characteristic of the lens. Personally I think Panasonic goes a bit too far with It's bright, bluish greens and skies in which the darker areas can slide into purple. But a lot of people like that sort of thing I guess.