Porkbits,
Welcome to the helo forum! Loaded question there. That depends on a number of things. Firstly, what model Cobra or Apache are you looking to build? For an AH-64 in 48th scale, the most accurate, best fitting, least fit-inducing is the Hasegawa both A and D models. Unfortunately, its also the most expensive, but well worth it.
As for a Cobra, you have several options, but unfortunately, all of them are out of production right now (although they aren't overly difficult to find on ebay). Monogram has an excellent AH-1S/F, Fujimi has a G, S and J and Italeri has a W and Z (really an AH-1-4BW). There's also an Aurora AH-1G which is hard to find, but not a bad kit at all.
Cobra Company makes incredible cockpits for all of the AH-1s in 48th and I highly recommend them. As for Apache aftermarket, Aires does great resin cockpits as well, although they tend to cost as much or more than the kits do.
Drop me an email if you've got any questions.
Jon