Okay, this was of concern for me with Kenny a while back b/c in his size Small FBs his scrotum seemed to be low when I changed him and there was a lot of heat. I have since learned that when relaxed a boy's scrotum will drop anyway . . . so that was a relief to know. There is a difference in heat though.
When Kenny goes to bed in cpfs and a wooly wonder or a fuzbomb I find that his skin is cooler, but clammier b/c of the moisture that touches him on the cpfs.
When Kenny goes to bed in a HH or an FB, his skin is not clammy, but is a bit more hot.
So, there is a give and take there, but I wouldn't think that there is a huge difference, though there IS a slight difference.