How really is FX better....

I have been reading that FX is better especially on the wide end.  But how?  Seems we have more cheaper, lighter, but still good wide lenses down -- 10-24 and even an 8-16!  FX does not have that many UWA  - just a few and they are heavy.

Granted FX will be better low light, better overall image quality for pixel peeping, and better DOF choises.

I have a D200 and am looking to upgrade - I have a lot of nice FX glass like 70-200, 105 vr, 35 f2, 70-300vr, 180 D 2.8.  My main DX investment is 10.5 fish.  I do shoot sports a lot but also tons of family stuff and vacations with the kids.

And I can afford FX - the main reason i dont want it is extra weight and size

--- For all those FX converts - is it fair to say that without pixel peeping or say on an 18x12 print with FX you get a little better IQ, thinner DOF, better low light. I have a feeling that except for extreem iso's that many shots would look similar (not as good but very close).

I mean in reality for non paid work whats the real difference for you?

Lately I have been using my Fuji X100 and the IQ is great up to iso 3200.  Its silent and that has real benefits that are not often thought about.  Sure iso 250000 would be great but i can pretty much get everything that is "meaningful" at iso 3200 and below.

So I want a D4000, but I was thinking of buying something like a D5100 for the meantime since its soooo cheap.... and wait.

Or do some of you have FX and DX?

thanks