You are getting two ounces less weight on the Proline according to the 2017 specs on the Redline website, and probably the parts on Proline are each mildly better than on the Mx24.

The Proline bike has a full chromoly steel fork, and handlebars. The mx24 mentions chromoly only for steerer, and the rest of the fork is thus likely to be so-called high-tensile steel. Ditto the handlebars, which are specifically called out as chromoly on the Proline. Brands will call out chromoly because it is a selling point.

Alloy cranks on the Proline versus chromoly on the mx24. Alloy is lighter in weight.

The above are items I notice from a quick look at the specs.