Actually, may 2 difference b/w K&N and Simota: cheaper ang Simota at mas matibay ang K&N (lifetime warranty). Sa design, halos pareho lang. Depende sa choice mo.

From my experience with Simota (i installed it in my Maxima, Sentra, and City), feeling ko e lumakas naman. What I did is a bought a K&N cleaning kit para ma-maintain ang effectiveness ng Simota ko. So far, they are doing just fine.

I think merong gawang Taiwan at Australia na Simota. As compared to stock, mas OK pa rin ang Simota. Test it yourself. Blow air thru the stock and Simota filters. Observe the flow volume by feeling it with the back of your hand. You'll be the judge.

Bottom line is, kung may budget kang malaki, go for K&N.