Okay, same question. Our external community needs a much more streamlined feature set than what comes with core. Would love to know how I can cater to both parties (internal and external). Ryan Rutan. And thanks for your time today, Ryan.
At a high-level, I recommend that if you are going to customize, it is usually best to customize forward than customize back. Taking time to actively suppress or get rid of navigation or hide experiences in the community usually comes back to cause problems. Users start discovering places you've missed or see other communities and start asking why they cant have that feature and so on. That being said, if you need to make these levels of customizations, then you need to be on-prem or hosted.
If the two communities belong with each other, and have a lot of cross pollination, then you are better off having them on the same community instance. You'll have higher return on engagement as well as time savings in simplicity when it comes to management.
If it were me, I would look at ways you can have both parties trade-off. For the cloud-users, try to negotiate away the need to simplify. For the on-premise users, try to negotiate away unnecessary customizations or defer to evaluate after the community launches and you have user feedback. Any customization you can defer to a Jive App is also a win.
In the end, I would try to error on the side of making it work in cloud, and assume that is where you are going until you are given a roadblock that you cant overcome. From there, if you run into issues, I'd recommend going to hosted/on-premise for both.
Definitely more factors to consider here, but in the end, there are so many positive benefits with cloud for those that can make it work ... Hope that helps. =)