Harder saddles are definitely NOT best for longer rides. I've been there.
The two most common pro saddles are the Flite and the SLR gel flow. These guys spend 6 hours/day racing, and NONE use Toupes or minimal carbon saddles.
I've owned the transam and now ride the SLR gel flow (Also tried the SSM Aspide and SKN, Toupe).
The transam is wider, and heavier. SLR works for me, but so does the San Marco SKN ($45!).
You need to know what width works for you, take this from your current saddle. Next, the saddle stiffness, which will depend on your weight.
Gel is better than foam padding, it does not deform, but it does prevent abrasions.