Wow... you really need to do some research man... The Commanche is a little more expensive, but it's much, much, much... better than the Apache. The first Commanches (prototypes) didn't even come out until about 10 years ago. For those of you that don't know how long it takes the military to implement vehicles: The F/A-22 Raptor's first flight was in 1997 and they are just now begining the mass-production phase. The design was accepted in 1990 I'm pretty sure. Anyways, the whole point of that is that there are few Commanches at the mement. It would be impossible for the Apaches to have already replaced them. The Commanches are currently in the production phase, and over the first few years of their service, they will simply replace the Cobras and Warriors. Their jobs then will be recon, quick-strike, and to feed the Apaches targeting data. When their numbers become greater, they will replace the Apaches.
The RAH-66 Commanche has a lot of stealthy characteristics. The radar cross-section is less than that of a hellfire missile (360x smaller than an Apache's, and 250x smaller than the Warrior's). This allows the Commanche to go places where other helicopters simply can't go without risk of being shot-down. The Commanche also lets off only half the sound of current helicopters. It also only radiates a quarter of the infrared heat current helicopters do. I'd say that's a lot more advanced than the Apache.
I could give you a lot of links, but there are few that sum it up well, as most are bits and pieces. This link is a little old, and only covers up to the first phase of mass-production, but it best-sums up all the others: http://www.fas.org/man/dod-101/sys/ac/rah-66.htm