I wonder if small dogs are more cuddly than large dogs. It makes sense in terms of heat preservation, but I wonder if it's true.
I'm not aware of any scientific research on this subject, and to really adequately answer this question you would need a study with a HUGE sample size and a way to objectively measure "more cuddly". For example, if you measured the time the dog spends cuddling, you'd have to control for the amount of time the people in the household are able/willing to cuddle. It could very easily turn into a huge experiment and be very difficult to analyze.
I suspect that there's also a huge amount of variation based on personality differences of each individual dog and the life stage of the dog (in my experience, cats get more cuddly as they age. I suspect dogs would follow a similar path).
If you want to select a dog breed/type who is likely to want to cuddle, I suggest looking for a rescue that does home fostering. Home fostering gives the fosterer a chance to see how the dog behaves in a home, and most of these rescues will let you talk to the foster to determine if the dog will fit well into your home and lifestyle.