Depends what you want to use it for.
We have an IT32 and its sort of okay for a bit of fill but not very powerful, cool little toy though and as you said if you have another camera system you can use it on both by buying another x5 trigger.
The V480 is very small and a lot more powerful so might be an option for you as well. It also has its own dedicated battery instead of the built in battery of the IT30 and IT32.
The older IT30 will do a similar job as the IT32 but you can't snap it of to use wirelessly like you can with the IT32 and you would also need to buy the riser as well so you don't get lens shading. The IT30 is far and away the smallest TTL flash, with the riser you can also bounce it as well. You can also ditch the riser if you are using smaller lenses making it tiny.
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Just to give you an idea of size thats a V480, an IT30 with the riser, an IT32 and a V860III to show comparison on what a normal size flash would be.
I often need a more powerful flash than the IT30 and the IT32 so the V480 is my favourite as it's a good bit smaller than our V860's and V1's so much so I will be replacing those with V480's. Plus I prefer the new touchscreen interface it is a lot more intuitive than the older system. V480 are also very cheap not much more than an IT32.