I'm reluctant to speak for Michael on this issue, but I think it is clear that both sensors, the FZ200 and the SX-50, are equally small and therefore both share the same disadvantages that are a limitation of all small sensors.
However, given this equal limitation regarding sensor size, there are other features of both cameras which are different, but very remarkable in their own way.
A 600mm/F2.8 lens is phenomenal, but a 1200mm/F6.5 lens might be considered even more phenomenal. It depends on your shooting style.
If you're in the habit of shooting static subjects (or relatively static, or slow moving subjects) on a sturdy tripod, then a 12mp image from a 1200mm lens should produce impressive results, even though the sensor is a bit small.
However, if one is in the habit of shooting static and/or moving subjects hand-held, or fast-moving subjects whether or not using a tripod, then the maximum f/stop of F6.5 could be a significant disadvantage. The final result may be no better, or only marginally better, than a cropped and interpolated FZ200 image at 600mm, F2.8 and ISO 100.
I recall about 15 years ago when I was getting interested in photography again, as a result of the digital revolution, I was amazed that Canon was offering a 1200mm F5.6 lens for full frame 35mm format, at the price of a small house in Australia at the time.
This lens was not available over the counter, but was manufactured only to fulfil specific orders from individual customers. I can't remember the exact price, but it was around the $100,000 mark, 15 years ago.
The fact that today a 1200mm F6.5 lens, which is only 1/2 a stop slower than F5.6, can be had for less than $500, and at a small fraction of the weight of the Canon 1200/5.6, is a remarkable technological achievement, even if the final result is not as good as that 16kg Canon lens attached to an 11mp 1Ds.
Just how much worse the 12mp image from the SX-50 would be, compared with the same scene from the 16.5Kg Canon lens with the Canon 1Ds which is close to 12mp, would be interesting to see.
By the way, having just compared the Canon 1Ds with the Panasonic FZ150 on the DXOMark site, I see that the DR of the FZ150 (which is presumably no better than the DR of the FZ200 which DXO have not tested yet, and likely worse) is equal to that of the Canon 1Ds at base ISO. All other measurements for the 1Ds are much better, of course, including the DR at higher-than-base ISOs. But the fact that the DR at base ISO from such a small sensor, (DR being essentially shadow noise in an ETTR exposure), is equal to that from a multi-thousand dollar, full-frame 35mm sensor of just a few years ago, is quite remarkable.
What is also interesting is that the ISO sensitivities for the Canon 1Ds and the Panasonic FZ150 are almost exactly the same, and both conform almost exactly to DXO's interpretation of the ISO standard. Amazing!