The Mobil 1 oil filter is well constructed and a decent filter. Unfortunately, I'm not been able to get my hands on a stock spec'ed Mobil 1 filter (but have taken apart a few oversized ones). However, I have been able to discern that it's made on the same line as the K&N filter, but will a media that is slightly better at filtration. Based on testing by others I still think this is a really good filter.
The AMSOIL SDF-20 filter is well constructed and lab tests show that it's an excellent filter. At 6350 miles this filter was able to generate the above lab test report and show that 10w40 oil in an H22A4 causes no problems. On the other hand, it's big brother the SDF-44 did not filter oil well at 13,000 miles. Proving that an oversized filter is not always a good thing when it comes to filtration.
The K&N HP-1004 is a great filter. The internal construction is the same as the Mobil 1 filter, but it does not filter the down to as small a particle size. This filter is meant to maintain higher flow while still actively filtering, as opposed to by-passing. Lab tests using Mobil 1 at 7500 miles indicates that this filter works as well as the AMSOIL SDF-20.
The FRAM x2 (and only the FRAM x2 Series) is probably the most heavily constructed filter I've seen so far. Though all of the Japanese made filters were of exceptional quality, the Fram x2 was as good in every way. Of note with the construction were the following features: metal screen backing the media, heavy metal end caps (all other Fram filters have cardboard), and 2 layer filter medium. Lab testing indicates this filter is fine at 5000 miles use with Mobil 1. As with all of the Fram filters and OEM Honda oil filters the x2 uses the standard spring loaded plastic by-pass valve that many people do not like. However, lab tests do not indicate that the valve jams or fails to work. It's possible that a hard enough impact at a sharp angle while the filter was by-passing might cause it to jam open, but I suspect the fluid within the filter would prevent this.