I have problem with them both. The greatest thing about role-playing is player choice. I find that in event baised, both as a player and as a DM, it is hard to feel like the players really change anything - the things that are going to happen happen. Site based has the same problem - the players walk to the place and whatevere happens happens. The great struggle I have as a DM is being flexable and letting the players guide what is going to happen. Then they feel they have a choice and are part of a living world. This is how they really seem to invest the most in the game. But I often find it hard as a player to have any idea what to do next without any guidance from the DM and as a DM to plan for or just deal with where the players are going to go if they really are given a free choice (and not to cry as hours of preparation get passed by).