ballistas or cannons vs units?

[Marius Dynamite]

In my Byzantine campaign cannons have just become available, so I only have bombards. So far I have been using Ballistas in my armies, they can really devastate enemy units. I usually only use the fire bolts and aim at the most elite advancing unit.

Bombard are fairly useless on the battlefield and seem to be only useful against Walls because of their poor accuracy. That being said I remember from playing custom battles that more advanced field cannons like the serpentine are much more accurate and retain the range. I think I'll go play custom now and try it out.

EDIT: I tried a custom battle and realised to my dismay that the Byzantines don't get the modern field cannons! (Is this true for campaign also?) Anyway I tried 3 French Serpentine Vs a force of 10 feudal Knights on grassy plain VH difficulty. It managed 151 kills, has a very long range but it quite inaccurate at the long range. I then tried 3 Ballistas first with normal ammo, it managed less than 33 kills (when they went into melee they got a few more kill, I forgot to stop it). With flamming ammo the result was roughly the same.

I'll admit it was a quick 10 minutes test, nothing scientific but it seems the late field cannons are far more effective than the ballista, although the cannons are double the price aswell. Should point out also that the Serpentine is the predecessor to the Basilisk, which is even more effective although I didn't bother testing, I imagine it would be very rare in M2TW camapigns.