I used a dutch gag on a horse before and it worked heaps better than a loos ring snaffle but my sister found that the same horse went better in a snaffle for her. Your question dosn't really have a answere. Every horse and rider combination work better with different things. Also what are you refering to as a regular bit?
A gag bit is very severe in untrained hands. Honestly if you don't know what it does then you should be avoiding it.
What is your horse doing that the question comes up?
I googled "gag bits" and came up with a number of articles. They all pretty much agree with my assessment about the severity of the bit. This is one of the articles: How to Use a Horse Gag Bit | eHow.com
Well, when I bought my mare she had a very hard mouth, so I've finally gotten her to respond and soften up a bit to a straight bar snaffle with a roller in the middle. But she still doesn't like to stop, and if she gets excited she runs right threw the bit. I want to try and keep her in some sort of snaffle if possible. If you think a gag bit is too harsh than do you think that some more softening or even transition exercises would help with stopping and such. I just saw the gag bit in a few catalogs and thought it could be a possibility.
I'm guessing an American gag bit is something different to a British one?
At my stables, a few horses wear gag bits - they look like this:
Usually the rein is attached to the large ring so they just work as a snaffle. However, with some horses that occasionally need a reminder to put their heads down, the rein will be put on one of the two rings below. This adds a small amount of leverage on the poll - not much, a ratio of either 1:1 or 1:2 - and it helps beginners who are gentle with their hands. Obviously the gag bit can also function in the hands of a better rider in a similar fashion to a double bridle, with two reins: one on the big ring, one on the little ones, so that you can select the snaffle or leveraged action as you need it.
But on Google I see things like these:
They look much harsher as they have much longer shanks. Are these what are thought of when an American refers to a gag?