Which is better? old Cosworth air filter or new 'regular' air filter
 

I'm collecting all the bits I need to do a service on my car including the cam belt and various other bits (e.g. tired looking rad pipes, rusty crossover pipe, rusty PAS cooler). One thing that I'm aware I've not changed in a while is the air filter. I've currently got a Cosworth panel filter in there that's 3 years old and done about 25,000 miles. I can't really justify the cost of another Cosworth filter on top of all the other bits I'm renewing at the moment, so was considering adding one of ICP's standard 'high quality air filters' to my shopping list.

This got me wondering - am I better off just keeping my old(ish), but still reasonably clean looking Cosworth filter, or changing it for a new, clean pattern part?

My gut feeling is that any new filter is likely to be better than an old one, regardless of what it is, but just wanted to get opinions from here first.