K&N and M1 filters are exactly the same, other then K&N having the nut on it. in an LS1 with headers, its near impossible to use a regular strap wrench, so for me, the extra $2 the K&N costs, over the span of 2 changes a year, its well worth it.
read this for a rundown on good vs. bad filters:
http://www.knizefamily.net/minimopar...nce.html#bosch
in short, good filters: Amsoil, bosch, KN/M1, wix, purolater pure1 or premium plus, and fram tough guard ONLY....regular frams suck.
bad filters: all other frams, delco, champion, penzoil, and STP