gm and ft
Higher ft means ur transistors can act as amplifiers till higher frequency as after ft ur gain becomes<1.
So inhrently SiGe technology can be used for very high speed circuits(may be100s of GHz).But that in case of CMOS may be around 30-40GHz again depending ur technology and transistor length.)
High gm means higher transconductance and for transconductance amplifiers u get higher gain with them.)But the key advantage due 2 which CMOS is still surviving is it's inherent low power nature and high scalability.
Hope it helps.