I am assuming from your question that you are defining a drainfield as a system in which the lateral are placed in trenches while a leach bed is an area which might be the 10x40 foot area which is prepared and the laterals are placed inside this area. The key paramater to keep in mind is the total area of drainage available to your system. A trench system does require longer lateral runs for a comparable area of drainage. A 10x40 foot drainfield would give 400 square feet of drainage. You would need trenches 3 feet wide and a total run of about 130 feet to have the same area. Either system will work if installed properly and sized properly. Septic-Scrub can help in preventative maintenance when used on an annual basis, however if the system is only used a few months of the year, the rest will help rejuvenate the system.