Storj is much more better than SIA, there was like a civil war against the fanboys and fangirls about both companies, everybody was against each other because a lot of people were saying that SIA was much more better than storj.
Now they can see that all of them were wrong, sia is stucked at the same price that it was on August, and it is much more below of that price, i dont remember how much is it worth at the moment
Storj is much more better, not only on their products, the price of this altcoin has been increasing a lot too.
SIA has actually crashed a huge amount since August, it is now at only about 50 satoshis which may make it more worthwhile vs STORJ than a few months ago. However SIA still has double the market cap of STORJ so with that in mind you could argue that STORJ has more room for growth than SIA coin.