You are comparing apples and oranges. Some aluminum frames have large diameter tubing, which results in a harsher ride than a steel frame, but the one you have posted looks like it has regular diameter tubing that may have the same ride as a steel frame. More likely, the handling of the two bikes may be different if their geometries are different. In any case, I doubt you will see much difference with the type of riding you intend on doing. So, again, my advice is to get the less expensive bike.