My friend works for ford, in the mustang department, as a suspension engineer... and even though he offered me the X-plan that would get me into a mustang GT for less than my BRZ, I couldn't take the offer.
The OP says it all and I concur. The 5.0L is an amazing engine and having that kind of power is amazing. On the test drive, I went on a back two lane road right outside of San Francisco and was blown away. The Ford Sales person let me really rock the right pedal. However, on the way back to the dealership, there was stop and go traffic, and this is were i realized have 5.0Ls is not practical, especially as a daily driver. The feel of the Mustang was big, heavy, and brash... Not what I like.
Ultimately, I chose the BRZ (over the 2015 WRX as well
) because of the way the car made me feel. Yes it is under powered, yes it has a lot of first generation production flaws, yes it is small and unpractical, but I love the way it made me feel. The closest comparison I can think of is driving an older Mazda Miata.
The BRZ is a drivers car, plan and simple and the emotional response had me sold. I test drove the 2015 wrx, and it is an unbelievable machine. Everything about that car is perfect, but it does not create the same response.
I grew up in Maine, where it snows for almost half the year sometimes. Rear wheel drive was never an option for me until I moved here.
Power in the front. Manual gearbox in the middle. Power to the rear. Masculinity 101.
Thats my $.02