Render times are much longer in Luxrender, but you also get to change a lot of the lighting while rendering. In the example above you can turn off the desk light light completely, while rendering or even after finishing.

Luxrender also outputs HDR images.

Carrara vs Luxrender can probably be debated forever, like in other forums that have battling unbiased vs biased renderers. I just see it as an alternative tool that has some benefits and some disadvantages.

Kixum, try your new scene in Luxrender, I'm guessing the results will be similar...