"I'm confused. Why did you ask the question if you had already decided that only one of the two possible answers made sense?"
For a number of reasons. I wanted a coherent argument explaining why this is. Note I am not committed to one of the two answers, just curious why the rule applies to this circumstance. If a silent, stilled, componentless spell with a ranged touch attack was cast by a paralyzed unarmored mage, would this be less inhibiting to his attack roll than if a mage was armored? As we know there are no shortage of minor oversights, errata, reinterpretations, etc in 3rd edition in no short part because of unforeseen circumstances. It would be easy to quote the relevant passage and say "because it is written as such", but I wanted to foster a more searching inquiry into the question.
Does the aim suffer because of the effect of the unfamiliar weight on the body? Or perhaps its the cumbersome nature of the armor throwing off timing? If so, why are spells devoid of somatic components unaffected by spell failure? Surely the careful precise patterns of hand gestures would be more prone to disruption than looking at a target and willing an effect toward it?
I thank you for any input you may have to clarify this issue.