The AI is so inept with missile troops that I always sally. I always keep a missile unit or two around and start the war of attrition immediately, because I can't win the melee fight in most of these. In 95+% of sallies, even against much larger AI armies, the AI will try to turn away and set up farther from the city. The AI army is very vulnerable when it does this, so I rush archers/slingers out and close, which allows them to fire into the rear of withdrawing heavy infantry. A cav unit or two can also be used to make units rout or pick them off if they break.

I send out some light cav or family member in support of the missile units, so that I can successfully withdraw the missile units if things get hairy. I will also use any cav I have to chase down onagers and such, since they move too slow and get left behind before the AI has reset.

I usually have some spears available, and I will use these as a stop gap against cav attacks. I can actually tear up the enemy cav pretty well this way, since it tends to come in piecemeal.

Typical sally for me would be 2 slingers (or archers/horse archers combo), 1 or 2 units of spears, or moderate infantry, 1 family member, maybe 1 or 2 cav/mounted javs (if I didn't have hrose archers for missile troops--if I did then I probably wouldn't have any foot archers or foot slingers.) Typical force size is about 5-6 units total, often facing 15+.

Assuming a large enemy force, with my missile units and opportunistic cav attacks I seek to kill off at least 2 and usually 4 enemy units in my first major sally. Then, when I run out of ammo, I go back inside and take the draw. On the next turn I do the same--and if I have a bit of luck I can win on the 2nd sally. If I haven't got enough edge left to win the melee on VH/VH, I will instead withdraw again to take the draw. By the 3rd turn I am always am in position to win in the sally (or in defense if the enemy assaults.)

Rarely some major blunder will happen and I lose a sally. If I don't have enough missile units to win in time, I'll send in some relief units to produce a successful sally.