Some will find Tripoli a bit dull. There might not be much more happening in Benghazi, but there is more movement. Afternoon life, and early evening life. For both sexes, all ages. Benghazi has more of the relaxed attitude Arabs are known for.
People hang around, look at one another, talk, and enjoy life.
Benghazi is a big city, far more than half a million. But it remains architecturally attractive, overlooking the sea and a marina, and many beaches make up the coastline. Most of Benghazi are modern buildings, but the old city is good, with covered alleyways. It's especially crowded on Fridays, when people fill the streets, shopping. This should be your leading star when staying in Benghazi, follow the crowd shopping.