Which type is better?

I have noticed that most of our members are strength coaches and that you have probably expreienced many different body transformations from students over their high school years.

What body type seems to have an easiest time building muscle?

That is a tough question. I would say the body type that really eats like they want to gain weight. Eating is the biggest problem. Many kids think they eat a lot. They really dont. Whenever they tell me they cant gain weight I ask them the following questions.
Me:Eat more food
Them: I eat all the time and still cant gain weight.
Me:What did you have for breakfast?
Them:Nothing, but last week I ate 4 double cheeseburgers at mcdonalds.

You will gain weight if you consistently eat more calories than you burn. That means eating all day every day.

Probably though to better answer your question, it is the big skill body types in football. LB's, FB's, TE's, etc. I don't know why but that has been my experience.

I think it also depends on the body type of the kid... ectomorph, endomorph, or mesomorph. Nutrition is the biggest struggle I have with my kids. Most of them just do not have the resources to eat properly and are coming into the weight room on an empty stomach where I'm asking them to train at a high intensity for 60 minutes... they just don't have any fuel in the furnace. Not a day goes by that I don't get on a soap box about eating.