I personally go Swadian every time, in my experience they either kick ass and become unstoppable *cough* trump train *couch* *cough* or get torn to shreds.
But the main reason is KNIGHTS!!!
I have modded so troop numbers for everyone are higher, and I go marching about with 100-300 Knights. They are unstoppable! I have gone through thousands of enemies (not kergits, they are the only troops that stand a chance - they only lose 3/5 to one) and lost ~40 men.
They are unbeievably OP. It's ridiculous, and the difficulty i play on (it's not super high, I'm not bragging) friends don't get health bonuses. I mean really, they absolutely kick ass as cavalry in the feild, they ride in and overwhelm an enemy formation in seconds taking no losses often. But as infantry in seiges they can hold their own against anything. (Huscarls give them a run for their money - but only when Knights are dismounted)
Really, I'm not exaggerating anything. Often my army is literally just Swadian Knights, they are so good.
Edit: Your party is also very fast if it's allc avalry. I go about with 600 Knights currently. (I modded with TweakMB) and I go at 6.1 in daytime on plains.
They also are effective against your wallet. 45 denars a week (or 35 maybe, either way costly-AF) burns through money.