This depends on what you're looking for in a game. If you just want to play by yourself and not have to worry about anyone, then obviously open pvp wouldn't be fun for you. However many others enjoy the constant risk of someone coming to kill them. It adds a certain thrill to the game to know any of those 10 people standing near you might decide to attack you at any time. Needing to constantly be alert, and ready to fight back with no warning. Obviously there are pros and cons, and some players will like such a setting, and others will hate it.
Obviously closed pvp is much different, since no one can just attack without warning, and those that aren't interested in pvp don't have to participate.
It's all a matter of preference. Some will love the open pvp games, some will hate them, and that's fine. In this case ffxi is not really balanced for any kind of pvp.