Just because they changed the filter milage rating doesn't mean they actually changed the filter. It just means they changed the marketing (companies do this more than you would like as a consumer). I may have read something about the end cap being different, so it might be true that they changed the design. I was just asking if you knew for sure or not.
The cheaper Fram filter design dates back to around 30 years ago. You can google about peopling cutting vintage ones open. They have actually changed very little, maybe they changed recently, but probably not by much. The design has proven to be quite reliable.
Yes those are all important, but you missed a big one—pressure drop. More pleats/area with the same filter media means a lower pressure drop. This becomes more of an issue with worn engines at idle, like the flickering oil light some people experience with older bulls. I tend to believe the basic FRAM with fewer pleats/area will create more of a pressure drop than some of the more expensive filters. No I don't have very much empirical data to support this other than reports of people switching to a different brand of filter and having their flickering oil light go away. Some of that might have to do with the filter being dirty or the oil being the incorrect viscosity.
Fram filters have a bypass that's very easy to open, I think it would bypass easier than a purolator. If I'm correct, the flow might be even better with a Fram, espically during a cold start, when the bypass needs to be open for proper flow. My main concern would be if it filters less because of the bypass.
Yes, they are ISO certified (I know what it means), but that doesn't change the fact that cardboard caps are less durable than metal. Whether that matters during the typical service life of a cheap filter is debatable. I would guess that the vast majority of FRAM filters do not leak during their lifetimes, but I've still seen pictures/video of the cardboard end caps separating on brand new filters. No, I can't be sure the videos are genuine, but I would tend to believe what I'm seeing unless proven otherwise. Their ISO testing should prove the filters are reliable enough, but does that mean they're as reliable as metal cap filters?
There is very little hard evidence that card board end caps are worse than metal end caps. I have researched this extensively, there's only really consumer speculation on whether or not it's better. Fram is pretty much one of the most popular filter makers in the world, and the failure rate can't be that high because there's only a few dozen or so failure stories on the internet. Nissian, Subaru and some OE Honda filters are made by Fram. There's also lots of examples of filters with metal end caps that have defects in the filter media.
Fram filters are generally fine, in my opinion.