King Cups!
Cups.
King of Swords doesn't give affection as a reward and so wouldn't withhold it as punishment. King of Swords would withhold respect and access to his mind. He'd use silence, a lack of word, not a lack of affection, to get his point across.
But the King of Cups...oh, dear. He's all about emotions and he will CERTAINLY withhold them from you if he's unhappy with you. Think of all those great dads who are the loving fathers, cooking dinners for their families, sitting at the head of the table, hugging and loving their children....And then someone does something really wrong and what does this King of Cups do? He turns his back on them. And it really really hurts because it was there in the first place!
You have to GIVE love to withhold love. What each king *GIVES* is what they will *withhold* to punish. Hence, the King Swords is more likely to withhold his respect, not his love. He doesn't give enough love for a withholding of it to have any effect as a punishment. Love (affection as it were) is not what he bestows on those he favors, and it's not what they expect of him, and so will be hurt by his withholding it.
Make sense?
P.S. In regards to that "long time" argument...I don't see how that's relevant. King/Swords may be able to be cold and unkind for a long time, but he could be that way for any reason. That's the point. He doesn't GIVE people enough affection in his daily life to make his withholding it hurt. In comparison, the King Cups gives so much affection that withholding it even for a little while is going to hurt plenty. It's not how LONG the king withholds it, it's how much it hurts when he withholds it. And in that, the King/Cups wins hands down.