Hello there @kennetherhabor!
Checking through the community, we can say there are tradeoffs in both ends. When you switch Niagara to GPU sim, you gain a lot in performance, but less in particle control from gameplay, collisions, and support on weaker hardware.
It would mainly depend on the need of your project, if you want better control over your systems, use CPU. But if you need thousands of active particles in your scene, go for GPU. I would also suggest to check UE’s documentation on the matter, and keep track of your performance for each configuration: