Question: For extended play through TOB, is a dual classed Magic User/Cleric or multi-classed Mu/C a better choice? (All other factors considered equal)

Ide say start out as a kensai and dual to a mage at level 12-16 if your planning on doing SOA into TOB. Then your just gaining spell casting abilities throught TOB. You have to understand that TOb is a much different game from SOA and magic plays a much more vital role, so youll be glad to be gaining spells at the rate you will be if you start as a fighter then shift to a mage. Maybe not the only way to go, but ide say from my experiance that its the best way to go

sorry i didnt see that you wanted to second class to be a cleric. in that case ide still start as a cleric then get to where you want to be at that class then shift to a mage. Healing is good, but when the dragons becons you forward to battle, your going to want to be packing some heavy spells to drop on him, or your going to end up as dragon fodder ;)

If it were me, I would dual instead of multiclass. With multiclass I just don't think that either class would get high enough level, because you have to split experience between the two classes. I would start out as a cleric and dual to a mage between 11 and 14 level.