Alright, so my theory is that when complementary Shards are on the same world, then all complementary shards produce "16"-based magics, while when no complements are present, "10"-based magics are created.
How this theory plays out in the books:
Mistborn: This is the obvious one. Ruin and Preservation are perfect complements, and they produced three 16-systems.
Warbreaker: Endowment is the only shard on her planet, so she cannot have a complement. Awakening has the Ten Heightenings, and there are five forms of BioChromatic entity (Vasher missed Spontaneous Sentient BioChromatic Manifestations In a Living Host in his explanation).
Stormlight: There are three 10-based systems here (Surgebinding, Voidbinding, and ?Lifebinding?), and the general consensus is that Honor, Odium, and Cultivation are non-complementary.
Alcatraz: Rutabaga.