Based on previous threads, you should get a lot of disagreement on your question.
Here is a link that tested the effectiveness of various air filter types, done with state of the art equipment. It is significant in its comparison of KN type filters, to paper elements:
http://duramax-diesel.com/spicer/index.htmI use a cheap stainless steel mesh cone with a cotton element, oiled with KN filter oil. It is a very good filter, for rocks, pebbles and twigs. I use it anyway because I like the intake noise it provides.