I'm debating between the 1940's shield and the 1960's shield. The draw for me on the 40's is that it is more limited (which is always cool), and it is more unique in that he only used it during WWII so people will probably ask about it. I also like it's crate more. I need to hurry up and make a decision before it gets made for me!
Once the movie hits, the 1960's version will be gone just because is more recognizable regardless of there being slightly more of it.
SLF,
That's solid advice, but I'd like to add that once the movie hits, there's a 99.9% chance that there will be at least one more replica of the shield available.
The round shield is so iconic it would seem a no-brainer to go with that one, but the knightly shield is very classy. I dare say that I think that it has a nicer visual aesthetic than the round one, even though the round one is the icon.
If someone could only get one, it's almost worth waiting on the round one, for there should be another offered by 2011 (that's the release date for the Cap movie, right?). Who knows if we'll ever see a 1:1 scale original shield again.