GunGame5 is much faster than the other versions, has less issues, and a team of people prepared to fix any issue you may find. There is also no downside of upgrading to the required EventScripts 2.0 as everything is backwards compatible.
If you still choose to run GunGame 3/4 remember that if you find issues we will most likely suggest that you upgrade to gungame5.
GunGame 4
GunGame 3