When it comes to conventional wood beams, while looking nice, they are also extremely heavy, which makes it difficult to move them around. Installation is a tough ordeal for those who are doing it. They require a lot of maintenance, since they can fall prey to cracking due to excess moisture. People who use these often find themselves making repairs sooner than they would like.
Box wood beams are hollow, which makes them significantly lighter to carry around and position to install. They are also not likely to have any issues with cracking or moisture. Installation tends to be a lot easier, too. People get a lot of good use out of these in their homes.