Hi and welcome. Benham has made some very good points, so there's not much to add.
The only thing I'll say is that if you buy a 2.0, you may later come down with a case of cylinder envy. It's very unlikely that if you buy the V6 from the off that you'll regret it - as the only real cost difference will be all of 5 or 6 MPGs. I haven't driven the 2.0, but I'm guessing that the lower down torque that a larger engine provides suits the nature of the Cougar better - a good GT that doesn't handle too badly when you need it. That said, I'm sure the 2.0 is a great engine too, and I'm clearly bias being a V6er. Good luck with the search.
The only thing I'll say is that if you buy a 2.0, you may later come down with a case of cylinder envy. It's very unlikely that if you buy the V6 from the off that you'll regret it - as the only real cost difference will be all of 5 or 6 MPGs. I haven't driven the 2.0, but I'm guessing that the lower down torque that a larger engine provides suits the nature of the Cougar better - a good GT that doesn't handle too badly when you need it. That said, I'm sure the 2.0 is a great engine too, and I'm clearly bias being a V6er. Good luck with the search.