As you can see, height-wise, the metal Garrison figure is very close to his plastic brethren, though a bit on the well-fed side for anatomical purists. By the way, Garrison figures would go very well with those produced by MiniFigs I think since the two are very similar in height and build. The Garrison figure pictured here is also much shorter than his 30mm RSM or Holger Eriksson cohorts.
Now, for some gamers/collectors, these slight differences in figure size and dimension might seem problematic. However, as has been noted many times before in the Yahoo Old School Wargaming discussion group (and possibly other places too), if figures by various manufacturers are kept within distinct units, and not mixed within the same unit, the minor differences between them become less noticeable. That point is especially true if you have assembled your miniatures into LARGE units, which are what jump out at the casual observer.
Just for fun, I included a 30mm plastic Spencer Smith miniature and a 25mm MiniFig in this shot. Those of you who have followed this blog for a while might recognize these characters -- the craven General von Drosselmaier/Colonel von Grundig and Grand Duke Irwin Amadeus II, sans his dual left-clawed lobster costume!
Finally, here's one last comparison photograph taken from a slightly higher angle. Yes, delusions of cinematic grandeur and Orson Wells' noir masterpiece A Touch of Evil! At any rate, from left to right, are shown figures by: Zvezda, Revell, Garrison, RSM95, Holger Eriksson, Spencer Smith, and Miniature Figurines.
Bill, I hope these photos supply the information you requested. It's always fun to have an excuse for an exercise like this, to compare and contrast the products of different manufacturers. Ah, if only there were dependable money to be made doing this kind of stuff. The Grand Duchess and child-to-be might see Father change career oars in mid-stream!