Is the 383 a better engine, or does the 440 just have more displacement?

The benefit of the 383 is it's short stroke. With supporting parts, it can be built as a high revving engine to make great hp....if that is what you want.
Some claim that big bore/short stroke makes for better breathing because of the large bore. It is the intake valve size that is critical for power, not the bore size, because it becomes the choke. Just one example, 455 Pontiac has a long stroke, small bore [ 4.151"] but has a 2.11 intake valve; 440 has a bigger bore, but smaller 2.08 valve. Pontiac placed their valves across the bore c/line to get bigger valves in. Because of this, even the Pontiac 350 HO engine came with a 2.11"valve with a small 3.88" bore. Chrys BBs had the valve line offset from the bore c/line which limits valve sizes, unless you re-design the head.