Regarding the long filter (PF63) vs the short filter (PF48) or in Fram language, the long filter (10575) vs the short filter (10060), I did a a few quick calculations. Das-Peikko mentioned the actual filter in the shorter canister was only 2.375 " long. The length of the short canister itself, from the Fram catalog is 3.33 inches. That means the remaining length is for the spring and valve. So, 3.33" - 2.375" = 0.955". If you now assume the long canister has the same distance for the spring and valve you can take the length of the canister which is 4.06" from the Fram Catalog and subtract the 0.955" to get an actual filter length of 3.105. Take the long filter of 3.105 inches and divide by the short filter length which is 2.375, you get 1.3. Since the area of the filter is linear with length you can assume the long filter has 30% more area than the short filter. No big deal but if the filters cost almost the same, and there is nothing else detrimental about it, you might want to be using the long filter. Obviously the engineers had some reason to make the filter longer. Maybe it was just to get an extra 30% of filtering area.
SF