We've been struggling with the same debate. However, in our case all of our virtual desktops are persistent. We are working towards non-persistent and until we get there we are holding off on instant clones. We are also waiting to see what VMware does as they announced a few years ago that they intend to deprecate linked clones eventually.
You should factor in the other features that come with Enterprise to ultimately decide if it's worth it. I'd say it will always benefit you to be on Enterprise to have access to all features. You might also consider looking in to the new license model that allows for running Horizon both on and off prem.
I did not realize that VMware has talked about deprecating the use of linked clones. Perhaps it is time to make the jump. Here is the licensing comparison
We do not use RDSH, App volumes, or many of the other features of Enterprise Licensing. Really the only feature we would like is instant clones. This makes the decision tougher since we would be paying a lot of extra money for just one feature.
Instant clones are clearly the way to go but if there are no other compelling reason than hold off until you need it. Keep in mind that instant clones do allow you to drop composer which is often an additional server and database.
Not worth it.