Hi,
I may be able to help a little.
I am an old guy cat 3 masters racer.
I have the Venge Pro (not sworks) model with Ultegra electric and have trained and raced on it the past 2 seasons. It is a nice race bike. I would rate it is a little stiff but not really harsh. It is a good blend between the TT bike and road bike as far as steering and handling. I use 25 mm tires for most of my training miles on chip and seal roads with the wide HED rims which I think helps with the ride.
I would rate it high as a "race bike" which to me means quick steering, and solid handling at speed, also a good descending bike bombing down from the ski area. Race bikes are stiff and fast handling because the pros demand it.
I have rented the Cervelo S5 twice, once before buying the venge (S5 56cm) and once a year after buying my Venge (S5 54cm). My venge is a 54 and I am glad I ended up with the Venge after the Cervelo buy fell thru for me.
The Venge rides more like a regular road bike, the Cervelo more of a TT bike feel.
Those are the only 2 aero road bikes I have ridden. I also have an old TT bike which is why I am comparing the ride feel to as well as other road bikes.
I would test ride the Propel before buying to make sure it was a good all around riding bike. Test it up, down and on rough roads to make sure.
Don't get to caught up with the aero fast feeling on smooth roads and be sure it is a bike for all your rides.
I owned and raced a Giant SL2 advanced with ISP and it was a nice bike as well. It handled a little slower than the Venge and felt super stable on the down hill. I would ride a Giant again as far as product satisfaction.
I have also ridden and raced the Scott CR1 and Ridley Damocles.
Hope this helps and let us know if you get at test ride on the Propel.
Rob