Some of the OFX plug-ins do need extra power (CPU and GPU), just as the NR options in Studio need more power.
Other than that, you get more source file compatibility, a larger number of resolutions, and a bunch of other things. I can't find a comparison chart for 16, but here's one for 15:
https://documents.blackmagicdesign.com/SupportNotes/DaVinci_Resolve_15_Feat...
To me, it's worth the money, and I think the purchase price is very modest.
