Latency is dominated by physical distance. Every extra thousand kilometres between a player and your server adds delay that no hardware can remove.
Host near your majority
With a community split across regions, the instinct is to pick somewhere in the middle. That usually gives everyone a mediocre connection instead of giving most people a good one. Host closest to your largest group.
If both groups are large
Run two servers rather than one compromised one. It costs more, but a single badly-placed server tends to lose both groups over time.
Before you move an existing server
Confirm you actually have a network problem and not a server performance problem — moving region will not fix low tick rate. Our article on diagnosing latency covers how to tell them apart.