Combat daggers has a bit more sustained DPS potential than combat swords given equal gear and weapons. That being said, it's also a whole bunch more anoying, and just as boring (if not more). 1cp for 60 energy is the suck... great raid damage with just using SnD cycles... but my god it's not really that great for anything but raiding.
In any case, play what you like. Combat swords, in general, is better for trash due to the lack of positioning required. Yes, you should always try to be behind the mob, but for trash, simply being able to use your instant attack on crap that's always running in spinning = more DPS than the guy who's flying all over the place spamming BS (or mute).
I will admit, I always played combat swords at level 60. It was nice to be able to lead every damage meter while eating a sandwich, talking on the phone, doing homework, etc... with one of my hands. In reality, I was pretty serious, and I didn't do that sort of stuff often or anything lol. However, I do feel that since I've started playing mute, and using daggers in general, I've gained a decent amount of knowledge about the class. If you want to master the class, learn to play combat daggers efficiently, then play whatever you want :).