IMO Muwahid is a liability that's why I rarely train them. If you meet a bunch of Camels in the desert, these guys are toast.

Even if you survive, you have to protect them from fresh camel reinforcements or ghulams. Muwahids also can't soak multiple units and an invitation for trouble. If the AI managed to put two units on these, they break quickly.

With the Saracens, you are practically worry free. Just don't let the AI flank at the back.

In addition, you have to merge and retrain them again and again since they don't have enough soldiers (not very cost effective). Their casualty rate is high, just observe.