Why bother selecting only one material when you can have several?
Composite armors are made up of layers of material that each can absorb, reflect, or neutralize different types of kinetic and energetic impacts. Each layer can be specialized for different kinds of space-based interactions, and deployed as modular panels that can be replaced with (relative) ease. Furthermore, you need not rely on future materials, but instead on materials that are already well-studied an in use today.
Outer-most layer - Ablative (thermal soak, carbon phenolic) for dissipating high-heat radiation and slow down impactors
secondary layer - ceramics for dissipating the high energy of kinetic impactors
Tertiary layer - Explosive reactive armor to reduce the effectiveness of high explosives (large missiles) and defeat/redirect any impactor that has made it past the other layers. This also manages to generate deadly debris fields by ejecting the ceramics layer pieces as high-velocity projectiles.
Inner-most layers - heavy metal alloys (iron, steel, etc.) for structure, and to absorb large amounts of radiation
Of course, these can be rearranged to suit needs, and other layers can be introduced as needed for more specialization of craft. Each successive layer will go further towards defeating those unconventional attacks as well.
Exactly how this armor is deployed is pretty flexible as well. My mental picture is of the interior structure layer being mostly solid - forming the true hull of the ship - and it is surrounded by panels containing the other layers. Due to the reactive armor and ceramics, a strong enough impact or detonation will make a given panel or area of panels weaker or useless, and will require they be replaced. Automated ship repair utilities can make this a bit less of an issue, especially in combat contexts.
There are, of course, cons to this armor type, which deal mostly with great overall thickness and cost. That being said, cost is not an object, and thickness would come secondary to protection on a multi-billion dollar space vessel.