As awesome as MultiSite can be, it’s certainly not always the answer to this situation.
A first glance, you have the advantages of:
- One install (easy to upgrade)
- Easy to manage (with the help of the single sign-on plugin)
- Plugins & themes are shared – again, easy to maintain & upgrade
But in retrospect, these can equally work against you – since everything’s “in it together”, upgrading the core/plugins/themes might break individual sites (depending on their setup). There’s no isolation like you would have with individual installs.
If you opted for a manager like WPRemote, you get the advantages of MultiSite’s “central hub”, but with the benefit of granular control.
Also weigh up the fact you’ll need to migrate all your existing sites initially, which I’d argue would require some time to set up & ensure everything is working smoothly.
TL;DR: Go for WPRemote (or similar).