Simple answer to your question, it depends.
Personally, I don't give a crap about the "push kids to get fresh air and do fun stuff outside instead of sit around inside" argument. Some kids like being outdoors. Some kids don't. Some kids like both. And so on. There is nothing wrong with not liking the outdoors or vice versa. I prefer being indoors in a dark room writing code to being outdoors playing sports (a waste of time).
Also, the responsibility argument, the "I just want what's cool" argument, the "spoiled brat" argument, etc. it's all subjective because none of us know your 13 year old as well as you do (I hope). When I have kids, I will make them work for things. It teaches kids that you need to earn things in life and you can't just simply ask and receive. So before you think about getting him (or her?) any new computer (or anything in life), first think about what messages, ideals, morals, etc. you want to send. If you're like my Dad, who wanted to expose me to computers, you would teach him how to build his own computer. If you want him to learn responsibility, work for things in life, make some of deal with him. Get straight A's, do chores, get a job, etc. to earn a MBA. And so on. You're his father. You're supposed to raise him to be a good man.
