[rick pearl]"Do they result in the same visual quality?"
Well... yes, but it depends on the application.
If you put gel on a lighting instrument, you change the color of the light coming out of that instrument. But if you put a filter on your lens, you change the color temp of everything. Sometimes that's acceptible and what you want, sometimes it's not.
Let's say you are shooting 250D daylight film in a closed (no windows) room, with tungsten lighting. You could put gel (maybe, say quarter blue) on all your lighting intstruments, but it would be easier just to pop a filter on your lens. But in a second scenario, lets say it's the same scene but with windows in the room that provide both a view outside, and some ambient daylight mixed in with your tungsten instruments. If you put that same filter on your lens, the tungsten lighting in the room will look ok, but the ambient sunlight and the view out through the windows will be extremely blue. In that case, best to leave the filter off the lens and put a bit of blue gel on the tungsten instruments.
It just depends on how you are shooting and what your lighting combination is.
Fantastic Plastic Entertainment, Inc. fantasticplastic.com
In any lighting design I create for video, approximately 99.9% of the lighting instrumentation has some form of color and diffusion in use.
A filter on the lens changes the entire color of the picture.
Through the use of color media, I can color every little element of my "painting" to enhance it however I see fit.