Wow, this thread xD So this is what I gather. Sasuke can use all 6 paths of the rinnegan, there's no reason he shouldn't be able to. We saw him use the preta path and the deva path already, these are confirmed. no need to ask if he has preta path. As to why he didn't use it in certain circumstances, outside of some situations where it was stated the rinnegan was recharging from dimension hopping, there isn't really a reason given. We've seen this kind of thing before though. The only one seen to liberally use all of the rinnegan's abilities is nagato. Obito opted to only use the outer path, and Madara only used preta, deva, and outer paths. Sasuke has used Preta and deva paths aswell. If I'm wrong about any of their path usage, feel free to correct me I have have missed something.
So not only sasuke, but even madara doesn't use all of the paths. why? The only logical explanation is that some of the abilities aren't useful to them. Madara did have the orbs after all, which are quite formidable. Like others have pointed out however, Sasuke has specifically chosen not to use the preta path in circumstances where it would be the ideal solution. So who knows what the hell is going on. I hate to say it, but without any explanation, it really does seem like Sasuke is being deliberately held back by the writer.
Oh and since this has turned into Naruto vs. Sasuke, I'll give my opinion on that. I think their last fight is all the evidence needed. It was a tie, and I think Kishi wanted their powers to be dead even, so I will say they are equal in power. You can argue this and that all day, but the fight you are arguing about already happened.