15 k, why a sporty?
Sporsters make a lot of sense in Sydney metro.
Definitely go a 1200, they are better in every way (besides CTP costs) can be lugged around and surprisingly rapid with the right mods.
However, if you do highway miles, the sporty will hurt after a while and the small tank (in particular the 7.9L on a 48) will mean 100km fuel stops and leg stretches.
I'm 6'2" and ride a Sporty 883 every day of the week. It my go-to bike for motorway riding as its light, nimble and stops on a dime (needed all that this morning when some dick in a Peugeot slide into my lane with no indicators and actually started to push me into the next lane - he had no idea I was there at all).
1200 will pull like a bat out of hell and lay waste to the majority of stock Big Twins so if your cashed up then go that route. and you really should be in the $10k region for cost rather than $15k ($15 will get you an older big twin, which will be heavier and a lot slower, but better suited for cruising)