Now that reminds me. I had this debate with myself before buying and ended up going with the 430 for two reasons. The 430 has an engine driven centrifugal pump for liquids but the 450 is gravity fed. The pump is critical for vertical spray height when pointing the nozzle up to reach up in the trees or eaves and soffits. With the gravity fed 450 the spray will stop if the nozzle end is elevated above tank height. I also read that a bunch of people were having problems with the tank leaking because it has to be removed and turned around for granules and then back for liquids. Eventually the tank-to-body seal leaks. I went ahead and decided that any herbicide or fert I may want to use is usually also sold in liquid concentrate form. For anything else like a seed or time-released weed and feed I bought a good drop spreader.