Dazzy,
Well to put it simply there are 2 questions that you have to ask yourself, the first being Portable or Desktop? They both have their own Pro's and Con's but it's fundamentally important to get this right first.
Do you need to be mobile?
The second important aspect you want to get out of the way is what are you going to be using the machine for? I know you mentioned a bit of everything but you will have to narrow it down a bit. I like putting machine use into 2 categories: The Administrative Machine, This is a machine that everyday end users should get. they would use it for Office, Internet, Email, Playing with their personal photos and making a home DVD. Perfect. If this is you I would suggest the Middle End Macbook 2.4Ghz on the portable side and on the desktop the Entry level iMac 20'' (Suggest putting in extra memory to have 2GB) on the desktop side. The main difference with the bigger 20'' is mainly the graphics card gets bumped up nicely.
The other category is Pro-User. This person needs a bit more grunt out of their machine, anything from Graphics Design right through to possibly making reasonably Hi-end movies. For this the Macbook pro 15.4'' or the 24'' iMac would be great.
In the end the iMac 20''s have a screen flaw that the Professional color conscious designer would hate. The 20" is a 6 bit-per-pixel TN panel. The 24" is an
8 bit-per-pixel panel from what I recall. TN panels are not as good for off-axis color consistency. Although they generally have better refresh rates their color accuracy is to be questioned... So if color is important to you then I would re-evaluate what iMac to go for. The color difference to the untrained eye is not noticeable, so if you are creating Websites or Business cards etc.. then you will be fine on the 20''. If you however are a professional photographer or a Pantone junkie then the 24'' is for you!
On the notebook side a similar color "flaw" exists and that is in the Macbook having a glossy screen. Although this makes the color look ever so vibrant on the screen when it comes down to the accuracy it has the same questions the iMac 20'' have...
Overall there is defiantly Pro's and Cons switching from PC to MAC. First of all there is a learning curve of some sort. Apple does having exactly what Windows does + more but usually has a different name or is located in a different and easier to find spot.. For example we don't have "The Control Panel" we have "System preferences" We don't have "A Start Menu" We have the "Dock" so I would suggest going to some sort of beginners training class or leaching Apple's website for the real basics. It's less than a hours worth of training needed to get you well on your way on a new Mac.
Another thing to understand is the dreadful rumor of COMPATIBILITY. There was a time in Apple's life where this was a major issue. I can now comfortably say there are NO compatibility issues with using an Apple! 90% of the time there is the MAC alternative to the Software you are using, might not be by the same name but it will do exactly what you want. Typical example as mentioned above is Microsoft Office (Word,Excel, Powerpoint etc) You can't go put your Windows version in your Mac and expect it to install, you will have to get the Mac version of Office. Exact same products and very little/no learning involved to how you use it!
Then there is the aspect of that one or two Windows App's that only run on Windows, then you can use Bootcamp (Which comes free with any Intel Mac) and a copy of Windows XP or *cough* Vista *cough* and install it on your Mac to have a dual boot.
I hope I haven't blabberd on here and that this is useful information to help you with th purchase of your new Mac. Please gimme a shout if I can be of any further assistance in helping you decide.
Good Luck! and i'm sure whatever Mac you choose it will take good care of you!
