mere

Light and L are close to equal when it comes to smarts, but from my perpective L is far more intelligent. You must admit that the fact thet L figured out that Light was Kira from the beginning was pritty amazing. Also although L died before Light it was only because Light had a major advantage, how can you fight a shinigami, also being able to kill with just a name and a face is very unpredictable. It is impossible to avoid being killed this way, in L's position anyway.

In addition L is a top-notch detective in his teen years, he has great detection skills (obviously). He even went so far as to reveal himself to Kira to provoke a reaction. That was definitely risky and probably the reason why he ended up dieing in the long run. If you ask me that was his first mistake, he made it clear to Light that he would be watching him from then on, if light was not Kira it would have been useful but in this case it was probably not the way to handle things. After all he didn't get much of a reaction out Light anyway.