would be worth taking a look at http://www.fiddleforum.com/fiddleforum/index.php as that's a really friendly place with lots of electric fiddle players.
My 2p worth - you might use an electric rather than acoustic fiddle for the same reasons you might choose to use an electric rather than acoustic guitar. My experience of playing an electric fiddle is that if you simply want a loud/amplified acoustic sound then then are ways to mic an acoustic fiddle that might work better then using an electric - beacuse an electric is a different beast to an acoustic and doesn't behave the same way. Mooh is right, overtones & nuances do get lost (partly because you don't get the same dynamic range - you can't get the extremes of loud & quietness). The times I've seen electric fiddles used to best effect have been when a lot of electronic wizardry has been used to enhance the sound. Try getting hold of a recording of Ed Alleyne-Johnson (sp?). Basically, the gadgetry allows new avenues to be explored and can more than make up for the things that are lost. I don't think its better or worse, just different.

That said, I'm mainly talking about purely elecectric fiddles. For an acoustic/electric it may be that it's closer to an acoustic, although I'd still argue that if all you want is loudness& amplification then a microphone would be a better option.

Jess