Opportunity Cost effect on benefits My question is the following:

Let's say a person has two career choices. He would be succesful in both, but in one of them he is slightly better and thus he will do better. So let's say career A will bring him a utility of 10 and career B a utility of 9.

So career A will bring him a 1 net utility benefit, due to the opportunity cost of 9 of pursuing career B.

Now suppose that for whatever reason, career B is not a choice anymore for him.

Is he now better off, from the fact that his net utility benefit is 10 and not 1? Why or why not?
If you measure how well off he is by his utility, then no. His utility is 10 in both scenarios.

The fact that career A is open to him increases his utility more in the second scenario than in the first scenario, this is what the "net utility benefit" shows you.