I recently checked the uptime of several large Lemmy instances and found out that the latency of Lemmy.world was roughly 500ms while the latency of other instances was about 100ms. I suspect this is due higher server load. The daily active user count of Lemmy.world is substantially higher than the other top instances.
EDIT: The numbers
The daily active users (somewhat outdated):
lemmy.world response times
beehaw.org response times