Well honestly towny is very different than griefprevention.
Towny on the surface is the same as griefprevention with a bit more flags but easier to bypass but then when you get a bigger playerbase the towny can turn into a less "intense" version of factions as the nations go to war with each other. Note that once the "war" period is over all griefed content is restored and the war can only go on for so long.
Where as griefprevention you can "siege" another persons claim but its more of a 1v1 type of thing if you enable it. Griefprevention is alot harder to bypass.
So its really up to you what type of server do you want to create?
