We have a client on JS 3.x and we are in the process of converting to the JS 4.x sdk. They are asking why they need to use a MapScene service vs a Feature Service with returnZ=true.
I'll I've really got is Better performance and better graphics. But that is not really cutting it when faced with haveing to go with Portal. [My understanding is that you need a portal installation to get to a MapScene - ignoring the Proxy "workaround"]