Dslr or compact system camera?

I'm interested in upgrading my compact long zoom camera (Panasonic Lumix FZ38/35).
So I'm between nikon d3100 kit and Panasonic Lumix G3. I like photographing a lot especially while on trip but also in birthdays, in nature and at night.
I have lots of reviews about both cameras but I still need an opinion as both cameras can change lens etc. Ok of course a DSLR is more flexible that a CSC but on the other hand CSC cameras are smaller with equal picture quality. I have found an internet store with good prices (www.simplyelectronics.net) and both cost 500 euros or so.

Any suggestions? Not only for these specific cameras but generally.

The Lumix is a super camera and so is the Nikon d3100.

Myself, I would edge with the Nikon because you could easier build on it with extra equipment, like lens options, flashguns etc.
That said, I do not know enough about the Lumix, other than that I do own a Lumix TZ-10 which is a great little camera.

Why not go to a store and try them both in your hand and see what suits you.

Nikon D3100 is an awesome camera for an entry level DSLR, in my mind Nikon's the best
I've had it for over a whole month now and I've taken over 2000 pictures already, I love this camera, the only thing is that the 55-200 lens that came with my camera doesn't have VR.
This is a great camera for someone just getting in to DSLR photography, as well as someone who has used manual 35mm film SLRs