Ok I am sure somone will put me right but I belive that Silicate Carbide (SICs)are marginally harder and lighter than the older Silicate oxide, but are also more brittle....so if you drop the rod on a hard surface they crack. Other big disadvantage of SICs is the price! Like most of the guys I dont think they are really needed as I have never had a silicate oxide ring wear out.
Just going slightly off track for a moment...did I hear it right that Shimano have got a heated rod ring now?!
The best rings were the old-style Fujis with luminous inserts. I've got these on a 20-year-old rod and they still aren't showing any sign of wear. The luminous collar was incorporated into the ring to act as a shock absorber, to protect the linings from damage if you dropped the rod.
Single leg rings are far more prone to damage if you carry rods on slings or sling them in and out of the car all day when you change swims, venues etc.
I'm convinced it's best to fork out the extra for decent rings. You can really feel the distance, especially if you use braid.