Terra Verde and Emerald Island were built by the same builder and are similar communities. The main difference is what side of Rte 4 you want to be on. Emerald Island is on the west side and Terra Verde is on the east. I can leave my home at Terra Verde and take Osceola Parkway (.75 toll) and travel with little traffic and be in Animal Kingdom in 10/15 mins. But that is Animal Kingdom and there are a multitude of places to visit in Disney World. Epcot is closer to Terra Verde than the Magic Kingdom. It doesn't matter where you stay because there is always traffic in and around Disney. Even when I have stayed on Disney property and rented a car and traveled to Animal Kingdom it could take me 15 mins to get to the park!! AND if you don't rent a car and use Disney transportation then your travel time can easily double - depending on the resort you have chosen to stay out.
I wouldn't base a rental property off of the community as a whole and the approximated "travel time"... I would choose according to which home/community is going to provide you and your family the amenities you are looking for. I would also suggest that you read real reviews on Trip Advisor. Terra Verde is consistently rated in the top three of specialty lodging in the Kissimmee area.
Good Luck with your decision!! You are making a great choice to stay in a rental home and up until 6 months ago I would have never thought that way. I have always stayed on Disney property until March of this year when I stayed in a town home in Terra Verde and now I won't stay anywhere else!!
Debbie