1/300-1/285 scaling?

How well do the different ranges scale together?

For instance, currently I have all GZG DS minis.
I'd like to add some GHQ Merkava's to my force.
Will these scale well?	I picked up some very
nice mini's from Eureka, beautiful figs.  They
dwarf my GZG stuff.  I'm now curious about
scaling between ranges for mix-n-match forces.