Really? What model, size and series were the two bars? Did you actually weigh them? I'm always willing to learn something.
I'm a big fan of Ritchey's WCS series bars and stems. In part, it was a hands-on comparison of the various Ritchey WCS products that convinced me aluminum is the way to go. GENERALLY, an equivalent sized Ritchey carbon bar will weigh out within 10g +/- the same size/model in aluminum -- and it will cost a lot more (about four TIMES as much).
I went from the Logic II to the Evolution SL, so it was actually about a 40 gram difference
I didn't get the carbon bars for the weight savings though..I wasn't happy with my hand position on the Logic II's and the LBS recommended the Evolution bars for the design, I ended up finding the SL for a great deal on ebay around Christmas so I jumped on it. For the record the hand positions were significantly better for me on the Evolutions than the Logic II's, the weight savings and general comfort of carbon bars were just a nice bonus.
I was wary about carbon bars too from what I read on here, but so far so good. I understand why people don't race in them because if they fall and their bars snap then they're screwed, but since I don't race and I haven't fallen yet I figure in my case it's worth the risk.