You can't go wrong with kids trundle beds. If your child has friends over on a regular basis or if a cousin comes to visit sometimes on weekends it is a perfect choice.
One of the greatest excitements for kids while growing up is having a friend spend the night. Having a special place just for their friend to sleep would make it even more exciting.
Besides the obvious space saving benefit of kids trundle as opposed to having two twins. Another great benefit that parents might not have thought of is that it eliminates the possibility of your kids stuffing all their toys under their bed when they clean their room.
Your children will have to be creative and find other places to stuff their dirty socks and uneaten food. The only down fall is that it eliminates the possibility of hiding under the bed during hide-and-go-seek. That's one of my girl’s favorite spots, but another positive note is that it also eliminates monsters from hiding underneath as well.