In today’s disruptive market Hybrid deployment is a key for any kind of IT infrastructure deployment. Microsoft provides Infrastructure as a service (IaaS), Platform as a service (PaaS) and Software as a service (SaaS) as their cloud offerings. O365 provides SaaS based offerings while Azure provides IaaS and PaaS. O365 offerings provide Exchange Online, Skype for Business Online and SharePoint online. If I talk about wave 15 products such as Exchange 2013, Lync 2013 and SharePoint 2013, I believe you can use full set of features if you have on premise deployment while all these products were tightly integrated with O365.
As we all know, Microsoft is moving and focusing towards mobile-first and cloud-first strategy. Therefore we can see more features are coming for online services and while few of these are not available for on premise deployment. If I discuss about Skype for Business Server 2015 deployment, as of now you can get all the features in on premise deployment except “Broadcast meeting” and “Cloud conferencing recording”. Below is the table which shows high level difference between on premise, online and hybrid deployment. (Courtesy: Microsoft)
As you can see in the above table, hybrid is the only option to get all the features. This is not only for Skype for Business, same thing you can see for Exchange and SharePoint.
Therefore, in short Hybrid is the only way to go.