Anxious preg,
when they can stand, the playpen can topple to the side, especially when they are trying to climb out.. so the bigger they are the more active they become, by that time, a playyard will be better for them.. just to share my experience..
I have playpen at home, my girl didnt like it, so it was kept swee swee in the box haha.. as for playyard i didnt buy.. normally just keep her occupied with some of the cubes/crayons/books when i want to do things..