Why would ANYONE even contemplate a game rated an 18 for a 14 year old!? I despair. Some 'parents' astound me and furthermore anger me because these decisions that you take to expose your children to adult material are fine, your child, your rules. But when your child with that exposure in their head, is around my child, you're making a decision for me too!
Society picks up the crap from the 'it never did me any harm' brigade.
OP I know you've asked for opinions and not yet purchased, please think carefully before and if you do. What may seem ok in your eyes, wouldn't be in the eyes of a 14 year old who doesn't have the cognitive or emotional maturity to view and correctly process such content. It de-sensitises them and makes a lot of unacceptable real life behaviours, acceptable - because it's a 'game'.
In my work I come across a lot of dis-affected and disturbed youths and all of them have many emotional issues and are also gamers from a very young age where all have had access to adult material long before they should have done.
I also work very closely with a Consultant Psychiatrist who prepares our expert reports for submission in Court, we draft defences and part of our defence is the youth in question has not had a stable upbringing and therefore has been unable to make correct decisions for him/herself as they lack the mental capacity for this.
Let me as you this, would you buy him porn for his birthday? No, so why is this any different? Content is yes but the rating is in place for a reason!
Don't do it and teach him respect for societal boundaries, they are there for a reason and will be beneficial to us all in the wrong run.