As I understand it, the term Boxer came from the pistons' appearing to be 'boxing' each other...what do you think Kuan?
Of these arrangements, a straight six is the smoothest. However, it's the least easy to package (which is why they're often canted over to one side) and potentially has the highest center of gravity.
A flat six works better than the other configurations for Porsche for a couple of reasons:
1.) Low Center of Gravity
2.) Air cooled
A V-6 is a great configuration for packaging, but is only smooth when including some sort of active balancer to get rid of huge 2nd order vibrations (whatever the heck they are-engineers please chime in here); virtually all modern V-6s incorporate a crank-driven balance shaft of some sort
As to Kuan's contention that a flat 6 would wear less than the others, I'd not heard that nor do I really understand why that would be the case. Anyone care to elaborate?
"If everything seems under control, you're simply not going fast enough" --Mario Andretti
1995 E500 street car
1986 Porsche 944 Turbo S track car