I have asked myself this very question many, many times, what if there was a law that you could only have 1 bike (perish the thought..lol).
The question I ask myself is which one??
I am a Peugeot fan and currently have 4:

1. Crazy Horse MTB which is used in the winter with studded tires, fenders, rack, coaster brake etc.

2. Canyon Express MTB which I use when I want to tear it up off road.

3. Urban Express which is used for commuting, grocery getting etc with full luggage, rack etc

4. PX-10 when I want to go FAST...

Love this thread