Magnetohydrodynamics - Plasma or Liquid more conductive?

[mikerand]

Sorry, I am not a physics major - I apologize in advance if this question is ignorant or if this was asked already.

What would be the most effective as a Magnetohydrodynamics weapon?

Assuming normal ionized air, would a liquid (liquid silver and salt water) or some type of plasma (anything?) be better for distance traveled and / or electrical conductivity?

Or is something else better than either of these?

I was playing a science fiction video game where a MHD weapon was used and there was a debate among my group of friends as to what would be best.

I just wanted to know what really would be the best for this. Thank You!

 

[Xforce]

MHDs are mostly used for propulsion, not weapons, they don’t work as well as rail guns.
But I prefer plasma for being accelerated by MHD, because I heard usually they have a negative resistance for electricity.