2.7L because I assume the Ford Performance tune for it will be much better and it's already starting out pretty far ahead in the torque department. It all depends on price though.
A friend of mine told me once, the bigger the battery the more vibration there isI'm getting 2.7. Texas highway speed limits are 70 to 80mph. I just feel the v6 will cruise better and won't buzz. At least that's the fact with motorcycles. Bigger cc less vibration.