Ariens Deluxe 24 differences

I'm on the Ariens website and see 2 Deluxe 24 models. 921045 and 921069. The only difference i see between them is Ariens AX 15.5 (921045) and Ariens AX 15.378 (921069) is there a real world difference? I'm wondering why the 921045 is only available online with a slightly bigger engine.