If you have the Studio License for DaVinci Resolve (Dongle or License Key), then you automatically have access to Fusion Studio. The standalone version of Fusion can easily be used together with Resolve and you can get the best of both applications.
The great advantage of using the Fusion tab in DaVinci Resolve is that is integrated and you can easily switch between Edit, Fusion, Color, and Fairlight. Also, most Resolve FX effects can now be used inside the Fusion tab. Likely the most important one for VFX compositing is the noise removal Resolve FX. For many artists, this temporal noise reduction will be entirely sufficient and remove the need for third-party software.
Fusion Studio is lacking the Resolve FX effects. But it still offers performance advantages. Lighter UI with additional options for floating viewers, faster start-up, better RAM usage, parallel branching, and network rendering through a render manager that can even be used locally.
Switching between applications is simple, so you can stay in Resolve for simple titles transitions or fast effects. When working on heavy shots for multiple hours, the roundtripping is not as bad as you might imagine. Simple ways to move back and forth include copy & paste of nodes or Import / Export of Fusion comp files – you do need to be aware of loader and saver nodes in Fusion Studio though.
If you use only Fusion studio for entire shots, you should consider using VFX connect. It links standalone Fusion compositions to Resolve and gives simple options for version management as well – you can actually switch between prerendered versions of a comp!
Yes, roundtripping means you need to render your Fusion comps before they appear in the edit. But that’s also what Resolve has to do behind the scenes to fill the Fusion Output Cache. You replace an automatic caching process with a conscious render process. Not necessarily a bad thing!
Are you using both applications? What is your workflow?