Here is a little more info concerning the "guts" of the M1 and K&N filters. Again, if you cut them both open (unused), as I have, you can see what's the same, and what's not.
Here are descriptions of the filtration media of each filter, from each company's website:
Originally Posted By: Mobil's site
Our advanced oil filters use synthetic fibers, which leave your vehicle with cleaner oil and an engine that performs better and lasts longer. When used with Mobil 1 fully synthetic motor oil, our Mobil 1 Extended Performance Oil Filter offers the best protection for your engine.
Originally Posted By: K&N's site
High-Flow Rate
Our oil filters use resin impregnated cellulose filter media. This allows for higher flow rates while providing outstanding filtration. High filter flow rates are important in racing vehicles where heavier grade oil is used and the oil is pumped much faster than in a standard vehicle. When the engine is circulating oil at high GPM rates, the high-flow oil filter helps reduce the loss of pressure through the filtering process.
In short, the two are very much NOT identical inside.