kenshireen

From what I can glean they are the same except that one has a whole in the middle.
Also, are these good for road bikes... They are advertised as mountain bike seats

lechat

They make a road version. The SI XC models usually have kevlar fabric on the rear sides for the inevitable MTB crashes. Otherwise the same saddle. The cutout can be good if you have numbness issues. As far as being a good saddle, they're well made. Whether or not it works for you, who knows? I tried 'round a dozen different saddles, in the beginning, before settling on Specialized. Toupe on 1 bike, Romin on the other'n.

Vetboy

I have one (XC flow version w the cutout) on each of my three road bikes. They just happen to fit my a$$ perfectly. YRMV

Clem von Jones

I'm guessing they're marketed for mtbs because of the extra weight and width, otherwise they have the same general design as the SLR road saddles. I like the extra width of the SL XC series saddles, just measured my SL XC Flow with calipers at 139mm. The non-cutout versions have more flex and some people find them more comfortable. On 130mm width saddles I can feel one of my sit bones slide over the edge occasionally, ouch! For road saddles you want one that isn't too wide but is wide enough to support your sit bones. You can measure your sit bones by filling a gallon zip-lock baggie with about an inch of flour, burping all the air out of it, and placing it on top of a toilet lid where you sit assuming an aero-posture. The one problem I have with my SL XC Flow is the the way the rails are attached to the upper causes a lot of creaking noise even after I've used silicone or teflon spray where they're joined. Maybe Selle Italia have redesigned this now but if not they need to. The imitation-copies of these saddles made by Velo (Senso-Miles series, look at Velo's website) are a little bit heavier but the rail attachment design is better. I like the hard foam used on both the original and Velo versions, Counter-intuitively, the thin hard padding seems to improve blood circulation.

thump55

I have one of those at home in white (with cut-out) that I'd like to sell. Bought it new, only used for two rides. PM me if interested.

EDIT: Just checked and mine is an XO Flow, not XC. 143mm.