When looking for a vibratory plate compactor it is very difficult to compare different manufacturers because they use different specifications to rate there plates. I have found two sources to make the comparisons of different manufactures easier. First is an article Light Compaction Equipment Specifications that explains basic information about vibratory plates. It is a little technical in nature but it does give you information on the process of how vibratory plates work. The second item is a calculator that will give you the ability to compare plate amplitude of different manufactures.  Both these references are put out by MBW Inc. They are the last company I know of that still makes vibratory plate compactor here is the USA.