I simply don't understand how a warrior culture could develop advanced technology. Yes, the Klingons would probably dump lots of resources into weapons development, but given that most Klingons are obsessed with being warriors, why would any be willing to sit behind a desk and research? The Federation's culture promotes research, and as such, would have far more advanced ships.
It's just that the Klingons we often see are the warriors and the particularly obsessed warriors at that. We've seen others, like Klingon scientists and lawyers and stuff. They're there, we just don't see them because the writers don't focus on them much.
In the Next Generation episode "Suspicions," Dr. Crusher talks about a Klingon scientist who is "defensive of her work, because her career choice isn't respected in Klingon society." ...This would indicate that yes, scientists exist, but they aren't respected in Klingon society.
As a result, the Klingon Empire should have inferior technology to the Federation, given that it doesn't have many scientists.