It all depends on the purpose of the laptop. Intel has always had better multi-tasking from their processors. They can divided it's own resources more efficiently and distribute power to all of the programs. AMD has moderate multi-tasking abilities, and are more easily overclocked. They will deliver more power to the current application (eg good for gaming) but you may notice a slight lag when switching between a large number of programs or switching between processor intensive programs.
As long as you aren't palnning to do major 3D rendering or video editing, the Sempron should be fine. I would suggest a mac if you were going to do this anyway.
Note that even though the sepron is listed as 3000, it will not be 3.0GHz, this is merely a comparison number. Under average conditions, the Sempron will run like an Intel chip of 3.0Ghz for the currently open application, even though it will post something closer to 2.5~2.6GHz
Hope this helps.