Mostly because the OP said he wanted to surf the web, and use email and itunes. Any old machine can do those things easily, so why not do it as cheaply as possible. If that's really all he needs, a g4 is more than fast enough.
Things like email and Im'ing mostly depend on his typing speed. If it takes an extra second or two to send an email, who cares? And tiger will work just fine for everything he wants to do.
Of course Tiger will work fine - but why spend money on not only old hardware but also old software when the newest stuff is right within reach? The iBook will still cost money. Also, in a few years, how much will that iBook be worth? The MacBook will undoubtedly hold its value better since it's a few years newer.
And yes, I do agree that lots of it depends on typing speed - but i'm talking about the overall snapiness of the machine - in terms of opening apps, actually starting up the machine, switching between apps, etc., - all this stuff will run faster on a MacBook, and it doesn't matter if the user is a new user or a power user - s/he will notice the speed increase.
Again - it does depend on the price - if I really wanted to go as inexpensive as possible and all I really needed to do was typing and was willing to go used - a $200 iBook would be a good choice over a $900 MacBook, but I don't think the price difference will be that large.
geez i don't know. i am just going to save up money for another month and see what happens from there but i really want to be up to date with the latest software not the older ones, and fast is what i want. i am a pretty fast typer, but that doesn't make any much of a difference for me. one more question i have is does the macbook have a brighter screen than the ibook g4? thanks everyone for all your help. i just don't know!!

kind of depressing lol.. i will mostly base my decision from now on, on the price, if i find a pretty good deal on the macbook, i will get it, i know that it is well worth the price.
The MacBook screen is supposedly much, much brighter. Read the early reviews (MacBook, core duo) - as these reviews make more comparisons to the just-then-replaced iBook G4.
If you want to be up to date in terms of software, the iBook would be a terrible choice since Leopard (or Snow Leopard) wouldn't run well or at all, period.
If you can, TRY an iBook before buying one - and then go try a MacBook. That will help you make up your mind. Truth is, though, that iBooks are rare now - since back in the PPC days Macs were much rarer than they are now. Now every second person has a MacBook, but back then it wasn't so. My estimate is that at least 90% of Mac owners are running Intel machines.