Tank
 

I agree with dommiek. Like the saying goes, "the bigger the better". Although the standard tank would suit my everday commuting and kickin' around my locale needs. The larger tank would be nice on long tours.

You can travel Australia on a cb250 if you wanted to! The only place you would need large quantities of fuel are the Cape York Track, Canning Stock Route and maybe 3-4 of the old desert tracks. There is always alternative routes. The canning stock route is an expedition not a track, and even 4x4's need to pick fuel up from remote aboriginal communities.

http://www.advrider.com/forums/showthread.php?t=116544

The above link is to a guy who had a blast on his 950 (~300 km fuel range) around Australia.