Hard to say why they made it smaller, but i would run either the Ultra or the Amsoil filter anytime before the Delco. The Ultra uses 2 ply synthetic media with 99.5% efficiency at 20 microns, the Amsoil uses a single thick layer of synthetic media with 98.7% efficiency at 20 microns. The Ultra is 80% efficient at 5 microns, which is superb, no one else even publishes these figures.
They are both higher efficiency and higher holding capacity than the AC Delco, but the Delco is certainly more than sufficient, just the other two are overkill.
The Ultra for my application was on sale for $5.30 on Amazon not too long ago and i stocked up, which is why they are the easy choice for me. If price was the same between the Amsoil and Ultra its a coin flip, but Amsoil is typically more expensive for similar performance.