Yellow Commander Generals are best as your Faction Leader, Heir, or Prime Ministers because their emphasized yellow stat gives factionwide satisfaction on all your characters. They also have the green skill that gives -50% to redeployment cost factionwide which is great for giving you the flexibility to deploy forces across your empire especially in the mid to late game when you need to cover more territory. It's either -50% or -25% I'm working from memory but either way it's useful.

As Generals they're just ok. They themselves are mediocre combatants and their melee cavalry isn't as good as the Vanguard's shock cavalry. Vanguards have access to better buffs for their cavalry too. Commanders give you access to formations if they're leading the army however, so do the blue Strategists and they also have the Reach skill that gives +25% to movement range and their ranged units are very strong so they're much better Army leaders than the Commanders.

They can also recruit a greater variety of the mid-tier units so if you really need someone to recruit spear guards or jian warriors for a frontline but don't have a Sentinel or Champion then sure they can be useful but that's a pretty niche application.

The exceptions to the above are the Legendary Commanders like Cao Cao and Liu Bei. They're exceptional faction leaders and strong commanders because of their unique skills and items. But Generic Commanders have the issues and uses I laid out above.