Helix they press the wire into a elliptical shape. Then they wrap the wire with the windings vertically to the core allowing for more windings across the length of the string. These are very flexible strings that also have heavily tapered wraps at the bridge.
Alloy 5109 wraps the wire at a higher winding tension so more windings are wrapped and less gaps are between windings. They also use a NickeL iron alloy that lasts longer.