12 inch PowerBook or 15 inch

there are two powermacs that I am looking at getting. One is a 12 inch 1.33 ghz that is going for $500 I was planning on doing lite FCP and DSP work on it but im not sure if it can cut it. Then theres the 15 inch 1.5 ghz that is going for $875 and it already comes loaded with office, fcp 4 dsp3, and photoshop. It even was upgraded to have a superdrive.

Now if I do go for the cheaper option would I be able to run fcp and dsp fine? I personally like the more compact 12 inch but I would not want to get it if I wont be able to do fcp and dsp stuff.

If you are worried about compatibility in the near future at all, get the 15" inch as it will last you longer, and run smoother. Having a larger screen would also be nice with photoshop, you aren't as limited with screen space.
Get the 15", just my .02 if the extra money isn't THAT big of a deal to you.