The Briggs tall, medium & short, & the 3 Kohler filters are all the same specifications wise they are just different sizes to fit in different locations.
Ditto for Kawakasi & Honda filters although they do have a few different spigot thread sizes.
I am yet to see a mower engine suffer any ill effect from dirty oil.
However I do see a lot suffering from too little oil or oil contaminated with water or fuel.
Now I will not argue the case that no filter is just as good as having a filter but I will argue that changing the oil is far more important than the filter the oil flows through.
I see many identical engine fitted to almost identical mowers ( different brands from the same factory ) both with & without filters and am yet to see any attributal differences in the wear between the two.
I have a motorcycle that is 100 years old in a couple of years.
I ride it more hours per year than most mowers run, it has no filter and still on std bore and original bearings & bushes ( mind you some of them are a little past due for replacement ).
Most motorcycles of the 50's & 60's had next to no external filters, ran around 10:1 compression, did 6,000 to 10,000 rpm and ran quite fine, provided you change the oil.
