The G-Loft Windbreaker and G-Loft Ultra Jacket are both light layers, but the right choice depends on what you expect the garment to do.
Start with wind and activity. A wind-focused layer earns its place when exposed conditions are stripping heat from an otherwise suitable clothing system. A light insulated jacket is more useful when you need a modest increase in warmth during lower-output periods.
Neither should be chosen in isolation. Consider your base layer, any fleece or shirt underneath, and the waterproof shell you carry for sustained rain. A simple system with separate jobs is easier to regulate than one heavy garment used for everything.
Fit is especially important in light jackets. Too tight and the garment restricts movement or compresses insulation; too loose and it can flap, snag and lose efficiency. Measure over the layers you will actually wear.
Also compare packed volume. A light jacket often spends part of the day in the pack, so its size and weight matter more than they would in a coat worn continuously.
Use the product specifications to decide between the two, not the photographs alone. Check current materials, insulation, pocket layout and sizing before ordering. If the job is mainly waterproofing, move to the rainwear range rather than asking either jacket to serve as a shell.