If you want to convert swf to mov, the iWisoft swf to video converter makes it really easy.That's what I use.

search for a program named iWisoft swf to video converter. It is a good tool

Looks nice.
Smaller size looks great.
I personally think the price will drop in the near future.

Try Nero.

It's all about compression ratios, and possibly also the size of the video (height and width).
Just like a JPG is way smaller than a BMP or TIF image.