We're talking strategus battles here. If you really believe a good cavalry player has more influence on a strategus battle than an infantry (as skilled as him), then I don't know what to say. That's not true at all from my experience. I would top all field battles as cavalry, but I could influence much more as an infantry pikeman or shielder.
And putting the cavalry on a rouncey (average horse) just makes it even more obvious
I have a more balanced opinion of strategus battles experiences.
It is right that a few very aware and dedicated spearmen can perfectly overcome any uncoordinated -or even organised- cavalry charges, but those few very aware and dedicated spearmen are not always here or battle-ready for various reasons (not rostering, battle time and duration, personal exhaustion, leader under using them, bad item selection, bad map).
Then if the cavalry opposing them is sufficient in quality and number, even those excellent spearmen wont be able to cover the whole battlefield, and the cavalry will be able to greatly support their infantry with bump and slash and backstabbing couchs/whatever.
Basically, I have had various experiences in battle where cavalry was present where the general feeling would range from :
- where is their cavalry ? (reading: not efficient for X reasons, thus raped and under-represented)
- their cavalry is raping us! (reading: efficient for X reasons, thus bumping and harassing greatly)
Also need to take into account cavalry vs cavalry metagame, sometimes even if you have good spearmen and "interdict" group of infantry to be bumped, cavalry can still rape YOUR cavalry, which will use up tickets and work in favor of a overall victory.