454 Compression Test vs Leak Down Test?

[savatreatabvr]

I known that a leak down test is good determining if the valves or rings are leaking and a compression test is good for determining how mush PSI the cylinder has. To perform a leak down test everyone says to bring that particular cylinder up to TDC and use the proper set of gauges to fill the cylinder with air. That's fine and dandy but isn't it more accurate to remove the valve cover and loosen the two rocker arms for that cylinder so the valves are 100% closed then take a air fitting and screw it in to the spark plug hole and supply air to the cylinder straight from the compressor and listen for leaks? A leak is a leak, who really cares how much it's leaking because any leak is a major issue right? If the valves leaks the head must be removed anyways so determining the actual percentage of pressure leaking is kind of irrelevant. So spending the money on a leak down tester is kind of pointless. Just my opinion.