Billionaire! No question.
While I'd like to be big, 10 is too big, in my opinion. I'd like to be 8 inches or so idealy, if I could pick.
But between 8 inches or a billion dollars? I'll take the billion!
I'm married anyway, so I don't need a big dick to get more girls, and I satisfy my wife just fine as is even though I think it would be fun to see her with a larger guy.
If anything, I could take a few hundred thousand dollar,s hire the world's foremost expert on penis enlargement surgery, and get my 8 incher the hard way, with plenty of money still left over.
Or I could just find the perfect well hung guy to fuck my wife on those occasions when she wanted a bigger dick, I could watch and still get off, and I could put that guy on my payroll as an employee with a larger retainer, or pay for his plane tickets/transportation back and forth whenever we wanted him!
The best of all worlds, lol.