If this is the case, why do you think that is?

 

Best guess is due to the clear lens and reflector.

I'm sure you could do this test easier than others and provide us a side by side.

I've seen it side by side only once against a garage door and the plastic output was much brighter.
That's all I'm going off of really.

Not sure the difference when driving/viewing signs I guess.

 

Stock Maxima lights just plain suck. Retros are better in plastic because glass has fluting that scatters the light IIRC. Im rocking stock glass with 9007 bulbs. I will say that glass wont haze and block more light over time.