Mega pixels mean very little once you go over 8 or 10. At that point it's more about the quality of the lenses. These 16megapixel compact cameras might seem impressive, but the sensor is tiny and the lens is small and cheap. But with a DSLR you've got a much better lens and better sensor even though it might "only" be 12mp.
You'll only see a problem with fewer megapixels when you print big images.
With a decent 6mp camera you can print out an A4 photo no problem, 8mp for A3, 10mp for A2 and so on. So, I would only be worried about lacking pixels if I was going to print out something say A1 or A0.
Besides, even on the highest resolution computer screen, you'll still only be able to show a 12mp photo at 20% of it's real size.
As for brand, I would go for the Canon, it's much more future proof, you won't be able to move up in the Panasonic range of lenses because they only have a small number. With Canon, there are hundreds of lenses available, some of them quite cheaply new or second hand. And chances are you will know someone who might be able to let you borrow one of their Canon lenses, but you probably won't know someone who owns a Panasonic with lenses to lend.
You can also hire lenses for Canon (and Nikon) DSLRs, so if you are going to a special event (wedding, etc) you could hire something way out of your price range for a weekend or week.
