I don’t think Giant Propel is an endurance bike. In my understanding endurance bikes are of shape Giant Defy and similar - top tube pointing up, handlebars at saddle level and so on. They are not designed to be fast, so normally aero/race bike would outperform them hands down in every way other than comfort perhaps. The difference between aero and race frames are more subtle, they have their weaknesses and strengths - there is right job for both types. One can gain free 10W going aero on flats and equally loose time cornering, climbing, etc.