Probably the biggest reason for using one of the 6$ flouro's from home depot is the ease. All it really takes is 2 screws in the marquee area to mount the sucker, plug it in and let there be light..
That's the big reason I did it, but I didn't have any existing wiring or electricals or bulbs or anything either. I have no knowledge of lighting like that, and limited electrical know-how in any case, so it was an easy choice for me.
One thing I did do however was to splice a toggle inline on the power cord, so I could relocate the on/off to a more convenient spot than having to remove my marquee each time