That totally depends on what station you want to listen to, and what direction that station is from your location. If the station is directly east from you, and your antenna is east/west, you'll get crappy reception compared to a similar north/south antenna.
If you have 2 antennas 90 degrees from each other and a switch, one of the antennas will always get good reception, regardless of the direction to the transmitter you want to hear. It doesn't matter whether you go N-S/E-W or NW-SE/NE-SW, as long as the antennas are 90 degrees to each other.