If you're talking about the Japanese accent, the main problem is that neither is the "right" way to do it. Japanese doesn't have r or l sounds. They have a sound that's kind of a combination of the two and is generally romanized with an r. The way I explain it is, "Think r, say l."

That being the case (cleans eyeglasses), different Japanese speakers will respond in different ways to r or l sounds. I worked with one teacher who had no problem with l, but couldn't say r. I worked with another in the same town who could say r, but had trouble with l. And there were some who never could separate the sounds, and others who had no problem differentiating between them. So, fail all around.