I don’t have experience on the tri style saddle, but have used the road Arione in both versions for a while now and can’t pick up on a difference between them. Most rides have been 1-3 hours with a couple of 4-5 hours on road bikes in a fairly traditional roadie position (both positions as identical as I can get them).
The oval (taller vertically) carbon rails don’t physically fit in some seatpost clamps and I think are better suited to clamps with a large support area to avoid point loading. Fizik claim that the carbon rails are stronger, but don’t mention what kind of stronger they refer to.
I would say that the weight is the only benefit.