https://www.networkworld.com/article...s-vs-saas.html
Both Azure and AWS have free tier for you to test out these are IaaS. These are basically replacing onsite hardware.
Both have certification paths, much like the old MCSEs or CCNAs. Certification is better than nothing especially if you are new to it. But things and offerings are changing so fast and on top of other vendors that leverages on these platforms, it's hard to keep up even for people who are working it.
Successfactors is a HCM product, that's more of an application or SaaS. So if you know your ERPs, Successfactors shouldn't be hard to pick up.
Big Data like cloud is just another buzz word. It's just analytic tools and reporting services on your data.