I suppose medium formats also have a greater dynamic range. Just as FX bodies have better dynamic range over DX. The larger the sensor the more dynamic range. And I'm not sure if I recall correctly but I think I read that there are no blown highlights or black crush with MF. Correct?
As for portability...now there are a few 24MP DSLRs. The D3x is targeted at studio photographers. Not too long ago if the ad photographers needed 24MP resolution prints they had to go medium format. Not any more. Though, now that there are 39MP and now a 50MP medium format I suppose they will request those resolutions.