When I had a commute similar to yours, I had a BMW with an A8 and enjoyed the more relaxed drive in traffic.
Now I live 3 miles away from work and it's all back roads with almost no traffic, so I went for an M6.
So, I fully understand your thinking on this matter.
However, you might want to check this thread and listen to the opinion to many Camaro owners about their Auto/Manual choice. There's also someone that picked an M6 for long commutes / heavy traffic drives, mentioning that the Auto was stressing his right leg too much as compared to the left one, resulting in more pain...
http://www.camaro6.com/forums/showthread.php?t=452508
__________________
2016 Camaro 2SS Convertible,
Nightfall Grey, MRC, NPP, Nav, M6