[DaveNP]

I think it depends on what you expect to do with it. I have a cheapo no name one which for the few times I've used it has proved adequate to show one cylinder was a lot down compared to the others, or I had nowhere near enough compression on all cylinders, or they were all within the tolerance. I can't think of a scenario where I'd need to know the actual value to high level of precision. The ebay kit appears to have a lot of adaptors and extensions so should be useful for one off tests on other cars too.