Minecraft world connection

Hey,

I run home server, and its time for update.
Currently I run 2 worlds, main world - survival and HungerGames world where my HungerGames are located to.
HungerGames world is limited to 300 block radius (600 blocks) cylinder.
Survival(main world) isn't bordered.

What I plan to implement into new update is 4 worlds:
1. Spawn - 180 block radius cylinder, and after is void
2. PvP survival 6000 blocks radius cylinder(or 12000x12000blocks) with world border
3. NOPvP survival 6000 blocks radius cylinder(or 12000x12000blocks) with world border
4. HungerGames 175 block radius, and after is void

What solution is better? Keeping the current world options, or go to new plan.
What do you thing will lag less, and is the 6000 b radius enough for server with 30-40(maybe after some time 45-50 slots)? Considering that there are 2 worlds, I personally thing that it will be enough, but I'm not sure about lag.

Any advice will help.

Thanks.
-DarkoMTC, server owner.