I was able to Model it pretty much to scale in maya without any issues. I mean, as long as you have something to scale to go by,
like mushroomgod suggested, you can't tell the difference. It may be a 16th of an inch off, but no one will notice.And by modeling it yourself, you have the ability to take out unnessary geometry on the botoms and tops of certain pieces, because when its all together, you won't see those pieces anyways. It helps to make your scene much smaller. And then you can take credit for the actuall modeling aspect. If you import everything, its hard to take credit, because you didn't actually model it, you just pieced it together. I don't know.. Thats just my opinion
If you are just creating something cool for an animation then by all means I would go with LeoCad. You can still take credit either way for the design aspect, and for "some" modeling.
btw mushroomgod, that is a really cool lego man