Sammie: AAC is a lossy compression format. If you rip to this format (or a similar one, like MP3) you are not creating a bit-perfect copy of the data on the original CD. If you want to create a digital music file that is guaranteed to sound the same as your CD, you are going to need to create a file with a lossless format.
Lossless compression is the way to go. An Apple-specific format is probably a mistake unless you are certain you will only use Apple hardware/software from now until the end of time. However, you can always convert from one lossless format to another without harming the data.
There is no reason to go with an uncompressed lossless format like AIFF or WAV, and anybody who says these formats somehow sound better than losslessly compressed audio is just plain ignorant (sorry, but there is no other way to say it...its kind of like saying three is not same numeric value as 3).