Cloud computing is massively transforming the IT landscape. On a pay-as-you-use basis, cloud consumers can access resources, applications and infrastructure provided by cloud providers.
If your top priority is security go for private cloud delivery model. If cost is a constrain and security is not that much you can go for public cloud!!
I think cloud technology is appearing to be the best and all the four above are good and they may be used for the purposes concerned and their priorities to be used.