It would be rather irritating trying to find the quests without the poi markers and don't forget that there are still some hidden places on the maps that aren't marked and which you often only find by going off the beaten path; so there is still an adventage to exploration. A compromise between the two options might be a "fog of war" style settup where sections of the map are only exposed as you explore and until you reveal them you don't see the markers in those areas. (save for the markers for missions you've picked up so you know what area you have to head into to fulfill that mission) Make the fog of war reveal large enough that you're not having to play mine sweeper, but small enough that it dosn't reveal a quarter of the map at a time ... a reasonable "line of sight" for your character as you move around.