Why is evolution more scientific than Intelligent design?

While evolution [as in the process] itself is a well established fact, the theory behind the mechanism of evolution is not. Many people [myself included] believe it is highly unlikely that life in all its complexities could have occurred without the guidance of a higher intelligence. This line of thought does not dispute the definition of evolution as “change over time” or that living things are related by common ancestry. However, we do believe that the natural world is too complex and diverse to have occurred through random processes.

On the other hand, many scientists and a large segment of population in Western industrialized countries believe that evolution is a random and not a guided process and that life spontaneously emerged from [again] random interactions of inorganic matter.

To quote Elie Wiesel Foundation Nobel Laureates Initiative: ”...evolution is understood to be the result of an unguided, unplanned process of random variation and natural selection… In contrast, intelligent design is fundamentally unscientific; it cannot be tested as scientific theory because its central conclusion is based on belief in the intervention of a supernatural agent.”

Now, the problem as I see it, is that both of these theories [random evolution and guided evolution or the so called intelligent design] cannot be tested as scientific theories as both of them stand on a central metaphysical assumption or beliefs, and not on observable scientific facts.

Or am I missing something and there really exists hard, replicable scientific evidence acquired through experiment and observation that proves evolution is random and unguided? If so can you direct me towards it? Thanks.