Different horses for different courses. I try to have my bikes set up for specific circumstances:

Specialized Roubaix Pro: all-day bike
Ridley Excalibur: fast bike
Soma Double Cross: winter/bad weather bike
Kona Sutra: commute bike
Specialized Stumpjumper Elite: mountain bike

But there really is no wrong answer here. If you want a second version of your present bike, go for it.