Well one thing to keep in mind that Electric will be easier to get up and running, as well as cleaner (chassis and components). If its a Family hobby Electric power makes it easier for all to have an easy access to get running. Nitro on the other hand require a little more support equipment, but in the end is very rewarding as well, the sound, smells and tinkering makes it so much fun.
Its a hard choice, id recommend going to a local track and watching a Nitro and Brushless race, to see perhaps what looks to be more fun for all, you will be able to see the pits and such as well, to get an idea of support equipment.
In the end you can not go wrong with either.