My experiences seem to mirror many of the other comments. There are pros and cons to each cycling environment. More often than not in my locale, urban seems to be more cycling-friendly for me.

Urban
- Lower speed differential
- More attentive and accomodating drivers
- Better connectivity and route options due to grid pattern roadways
- More intersection hazards
- More pedestrians and other cyclists (many of whom are unpredictable) to watch for

Suburban
- Higher speed differential
- More aggressive and distracted drivers
- More dead-end secondary streets, forcing me onto arterials
- Fewer intersections