Basically, the Extra is a more stable aircraft than the Cap. The Cap is better for some aerobatics due to its unstability, but the Extra can hold its own also.

If its your 2nd plane, I would suggest the Extra instead of the Cap. Or you may want to consider the Edge 540, which is very stable at low speeds.

Also watch out for the control throws you set up initially, as these planes are all sensitive. Use either dual rates or expo till you get used to the planes.

Being in Australia, you would be able to get the Phoenix models Scanner, which is a good low wing plane, stable and cheap. However it does not look as good as the planes you are interested in. But do keep in mind that you will want to avoid the Cap due to its inherent instability, but then again, if your one of those naturally gifted pilots, it may not be a problem for you.

Good luck and have fun.