Not to sound trite, but does it matter what is the hardest LL to learn? This is going to differ from person-to-person.
I think what Chrome was saying was in reference to Gift Giving being the easiest LL for my H to speak, and perhaps it is for Chrome as well in his own perspective. I'm not sure he was speaking in generalities. He was afterall responding to my post where I referred to my H constantly trying to buy me things...which doesn't work for me.
Can you tell me what you hope to gain by answering this question?