During all games where my team has had both Malian and Abbasid players, the Camel Support infantry armour buff and Sofa infantry speed buff have cancelled each other out, with only one ever being applied.
It has not been consistent which is the dominant buff, perhaps the one that is researched first/last?
This effect applies to all players on the team, with the same buff being dominant for both.
If for example Camel Support is the dominant buff and Mustofadi Warriors are standing next to a Sofa, they will correctly have the speed boost. If a camel also comes into range, it will lose the speed and gain the armour buff.
Quite unfortunate when these buffs are an important part of each units strength in a team or army composition.