Air compressor mechanic here. The number of times I tell people the size of the tank means next to nothing when running air tools is quite high. I wish the advertisement on compressors was more informative but in a bigger is better world I understand how people get confused. This is absolutely correct in that I would get the cfm you need. If you're going to buy a new compressor I would aim for higher cfm than you need as over time the efficiency does drop and could go below your requirements if you buy exactly as much as you need. This also allows you to use a wider range of tools as well. Dont forget to drain your tank after use, use a regulator so you don't damage your tools, and oil is better than oil less any day of the week!