1. Orion chicks in bikinis. Which morale officer would you choose? This, or this?
2. Attitude. All the species in the KDF are bad (70's bad, not sour milk bad). They're like a giant interstellar biker gang - and they know it. Give them a hard time and they'll be happy to personally demonstrate how a d'k tahg or disruptor works.
3. Freedom. Kinda related to #2. In the KDF the "tough choices" really aren't so tough. Someone dragging everyone else down with their incompetence? Execute them! Some peaceful alien ship have a warp coil you need to finish your mission to save the Homeworld? You take it! There's no hand-wringing or metrosexual mental dialog - you do what you need to do to complete the mission.
4. Practical. KDF gear and ships are mostly built for function, not form, and they're built to last. If a Klingon wants to pretty up his ship he'll decorate it with the entrails of his fallen enemies. Otherwise, if it works that's all the KDF needs. Why fix something that isn't broken? I mean, Klingons carry knives! Those things are really useful. Starfleet? No knives. They have red shirts, though. The KDF doesn't have redshirts. We have 'Execute for Incompetence'.
5. More believable. The KDF isn't a pie-in-the-sky pipe dream of the future. It's more realistic (comparatively speaking). They have pollution, war, crime, brutal politics, assassinations and social classes - just like the real world. The KDF isn't perfect, but it's not trying to pass itself off as perfect, either. Klingons hold honor in high esteem but most Klingons never live up to those ideals. They're fallible. It's as "real" as Trek gets for me.
Star Trek: Online - Now with 100% more dinosaurs!!