Here are my rankings. Feel free to critique mine or list your own. This is mainly for new players (if there are any more). I'll start by saying two things. One, that the factions are actually fairly well balanced, with the exception of the Khergits. And two, that your choice of faction is mainly a matter of preference and play style.
1. Swadians. Swadian Knights are the best unit in the game. They have the slight edge over Mamlukes because the latter sometimes spawn with unarmored horses. The faction is also very well-rounded, having no area in which they are really weak. Their infantry is quite good and their crossbowmen are adequate. Main disadvantage to playing Swadia is their location on the map.
2. Sarranids. Mamlukes are about as good as Swadian Knights, and their ranged unit is better than its Swadian counterpart. However, unlike the Swadians, they do have an obvious weakness, which is their infantry. But since infantry is the least important unit type, they are still number 2 in my book on the strength of their cavalry and archers.
3. Vaegirs. This was really close between Vaegirs and Rhodoks. I personally am a Rhodok player, but I have to give the slightest edge to Vaegirs simply for the fact that they have cavalry. Let's face it, cavalry is king in M&B. Their Knights are pretty effective. A notch below Swadian or Sarranid cavalry to be sure, but still a force to be reckoned with on the battlefield. The real reason to play Vaegirs, though, is the Vaegir Marksman, the premiere ranged unit in the game. Their infantry are generally regarded as the worst of all factions, mostly because of light armor and a lack of shields. They are very good in melee though with their bardiches. Just use your Knights to pounce on the enemy archers and you will have success with your Guards.
4. Rhodoks. If you want to play a no-cavalry faction, this is the choice. If played using a few simple tactics, they can be the best faction in the game. They excel in the siege phase, which is usually the most challenging. Their best troops are their Sharpshooters, which rival the Vaegir Marksmen for best ranged unit. They are better overall troops than Marksmen because they are competent in melee and wear better armor. The Rhodok Sergeant is possibly the best infantry in the game. Many people will think I'm crazy for saying that, but they have better shields and armor than Huscarls, who seem to die a lot more; at least that's been my experience. They will murder cavalry with their glaives, making them extremely effective against the biggest threat to your army. And as a little added bonus, they use blunt weapons. They also cost significantly less than Huscarls and train up a lot faster.
5. Nords. For me, this is the faction I desperately want to love, but it falls short. The archer is okay, but nevertheless he's the worst foot archer of any faction. The big draw of this faction is its infantry. There are two problems with that. One, infantry is the least effective unit type in the game. They have significantly less mobility than cavalry and virtually no range compared to archers/crossbowmen. Huscarls are very strong; however, they are not as dominant as they could be. They tend to die a lot due to using 2h weapons and slightly lighter armor than some other top notch infantry. They also cost a lot and take forever to train. The faction is so imbalanced between their infantry and archers, that it almost seems most efficient to build nothing but infantry. This is very problematic because of the power of ranged units on the field but especially in sieges using the standard cheese.
6. Khergits. I'm sure there are Khergit lovers that are going to get mad at me for this, but this faction is just bad. It's a shame, because lovers of history know that this faction should be greatly feared. There are many problems with the Khergits. For one, horse archery is just terrible. The AI doesn't know how to be a horse archer. Secondly--and this is also related to the dumb AI to an extent--armor is king. Mobility cannot defeat armor because the AI is not competent in using its mobility. A faction of nothing but light armored troops on light armored cavalry is just.... bad.
1. Swadians. Swadian Knights are the best unit in the game. They have the slight edge over Mamlukes because the latter sometimes spawn with unarmored horses. The faction is also very well-rounded, having no area in which they are really weak. Their infantry is quite good and their crossbowmen are adequate. Main disadvantage to playing Swadia is their location on the map.
2. Sarranids. Mamlukes are about as good as Swadian Knights, and their ranged unit is better than its Swadian counterpart. However, unlike the Swadians, they do have an obvious weakness, which is their infantry. But since infantry is the least important unit type, they are still number 2 in my book on the strength of their cavalry and archers.
3. Vaegirs. This was really close between Vaegirs and Rhodoks. I personally am a Rhodok player, but I have to give the slightest edge to Vaegirs simply for the fact that they have cavalry. Let's face it, cavalry is king in M&B. Their Knights are pretty effective. A notch below Swadian or Sarranid cavalry to be sure, but still a force to be reckoned with on the battlefield. The real reason to play Vaegirs, though, is the Vaegir Marksman, the premiere ranged unit in the game. Their infantry are generally regarded as the worst of all factions, mostly because of light armor and a lack of shields. They are very good in melee though with their bardiches. Just use your Knights to pounce on the enemy archers and you will have success with your Guards.
4. Rhodoks. If you want to play a no-cavalry faction, this is the choice. If played using a few simple tactics, they can be the best faction in the game. They excel in the siege phase, which is usually the most challenging. Their best troops are their Sharpshooters, which rival the Vaegir Marksmen for best ranged unit. They are better overall troops than Marksmen because they are competent in melee and wear better armor. The Rhodok Sergeant is possibly the best infantry in the game. Many people will think I'm crazy for saying that, but they have better shields and armor than Huscarls, who seem to die a lot more; at least that's been my experience. They will murder cavalry with their glaives, making them extremely effective against the biggest threat to your army. And as a little added bonus, they use blunt weapons. They also cost significantly less than Huscarls and train up a lot faster.
5. Nords. For me, this is the faction I desperately want to love, but it falls short. The archer is okay, but nevertheless he's the worst foot archer of any faction. The big draw of this faction is its infantry. There are two problems with that. One, infantry is the least effective unit type in the game. They have significantly less mobility than cavalry and virtually no range compared to archers/crossbowmen. Huscarls are very strong; however, they are not as dominant as they could be. They tend to die a lot due to using 2h weapons and slightly lighter armor than some other top notch infantry. They also cost a lot and take forever to train. The faction is so imbalanced between their infantry and archers, that it almost seems most efficient to build nothing but infantry. This is very problematic because of the power of ranged units on the field but especially in sieges using the standard cheese.
6. Khergits. I'm sure there are Khergit lovers that are going to get mad at me for this, but this faction is just bad. It's a shame, because lovers of history know that this faction should be greatly feared. There are many problems with the Khergits. For one, horse archery is just terrible. The AI doesn't know how to be a horse archer. Secondly--and this is also related to the dumb AI to an extent--armor is king. Mobility cannot defeat armor because the AI is not competent in using its mobility. A faction of nothing but light armored troops on light armored cavalry is just.... bad.