It comes down to surface area.
It won't matter if a filter is 99% effective if there is only one square inch of it.
If a K&N is a full size element with enough surface area to meet the engine's flow needs while filtering the air at 99%, then good. If not, then not good.
Most, if not all, of those "pod" filters that clamp on to the carb or TB are not even near enough surface area, nor do they provide enough free air volume inside the filter barrier for good throttle response or good atmospheric air pressure . If you look at them dirty, you can see that they flow mostly within the first inch, or so, of gauze.
A larger panel filter or round filter with plenty of surface area is much better, whether gauze or paper.