Looks and sound mostly.what is the difference between the type of air filters with the closed end and open end. For example, SPECTRE P2 CONE AIR FILTER vs SPECTRE P3 CONE FLAT-TOP.
You're not going to make enough power to outflow the cone. I've had both open and close top K&Ns and it's sound. The open gives more of a whoosh turbo-ish sound while the close gives a growling sound.
The open top cone does flow better but again when you're talking about 1200CFM and 1300CFM while you're engine only needs a max of 800CFM it's not going to do much for performance. (Numbers pulled outta my arse for example).