Symmetrical balance is the most immediately legible form: divide the composition down the middle and each side mirrors the other. It communicates stability, authority, and formality. It is the balance of government seals, classical architecture, and institutional logos. It is also, in the hands of a careless designer, the balance of boringness.
Asymmetric balance is harder to achieve and more interesting to look at. It asks the eye to weigh unlike things against each other — a large, quiet area against a small, dense one; a heavy dark shape against a lighter, larger form. Asymmetric balance is kinetic: it implies movement, tension, and resolution. It is the balance of great editorial design.
In screen design, balance is often an afterthought — something to check at the end rather than a principle to design from. The result is interfaces that feel either too crowded (no counterweight) or too empty (no anchor). Balance should be an early compositional decision, not a late visual correction.