Top loading kilns have the advantage of being able to load your projects from above, allowing you to more easily center your glass work on top of molds. In ceramic kilns, you can fit more ware and more layers, allowing you to produce more product in a smaller footprint.
Top loading kilns are economical and provide a huge value for buyers. When making a decision on a kiln configuration, always take into account the shape and size of your kiln shelf. the geometry of what can fit on your kiln shelf should influence your decisions.