A dipole cut for the frequency of operation will be about as efficient as you can get with a simple wire antenna, but the off-center-fed dipoles, wich is what g5rv and the like are, radiate well. I doubt if much directionality will be noticed by changing the antenna orientation at typical dipole heights (15 to 35ft), but if you can get it up a quarter wave or higher it will become more directional. That being said, what region do you want to cover?