Surprising, cause this is a very frequently discussed topic.
The thing is, live plants have their advantages and their disadvantages. On one hand, they take ammonia and nitrites from the water, which is very good. They also oxygenate, and give a natural look.
On the other, they create organic debris when they die that will need to be removed (but since you need to remove feces and left-overs anyway, this is hardly a problem), and they obviously need light.
Fake plants obviously lack the benefit of absorving compounds from the water. They don´t create debris, but might require some cleaning every now and then if they get covered in algae or slime (which is detrimental since you will eliminate the biofilm that grows on them). The plus of fake plants is the total lack of lighting requirements.
It´s in the end a matter of preference, although personally i think there is no contest (i´m a die hard supporter of live plants xD).