some advice i was given:
"the Army Special tyres are designed really for hard packed surfaces and for long life on smaller machines, the X Challenge being ok. The CO2 is also designed for hard packed surfaces, it used to be called the stone king before a CO2, it would be better than the Army Special but marginal on greasy rock surfaces, there again nothing works particularly well on greasy rock. The E-O9 is also a compromise tyre and more suited to harder srfaces and longish life. The very best tyre for wet, muddy, slippery conditions is the XT 754 size 120/90-18 but it will not last on the road, another option is the FIM Enduro tyres, the EF-07 in a size 130/90-18, these work well in all conditions, they use them in World Enduro Championships so down to you if you are not getting grip. The CO2 is a full on Motocross tyre, for commuting it will not last very long, I would go with the E-09"