I have the Flite, Flite Genuine Gel, SLR and TT.
The Genuine Gel is a bit thicker in padding on the nose down to the center (the perforated, stitched spot). From there back, it is about the same cushioning as the Flite.
It is comfortable.
I like the Genuine Gel, it's a good saddle. The TT is uncomfortable and the suede stains your shorts and the saddle looks like junk after a few rides.
SLR is really a good saddle. Comfortable as the Flite or Gel. I think for heavier riders, the SLR flexes too much under weight so they don't get the cushioning effect.
I use the Gel for a long time, but switched back to the Flite because they felt the same and the Flite was lighter. Maybe I'll stick the Gel back on to see how it feels again!
Anyway, if you like Selle Italia, the only one I won't recommend is the TT.