Laptop, if you know the key commands to switch windows you can "simulate" the experience of multiple monitors anyway. In addition, you don't have the added overhead of moving your head/eyes to focus on some other point, you just look at the same physical space in front of you while switching what is in that space quickly.

I also used multiple monitors for a time and found that the process of managing those monitors and all the open windows/applications etc to be more difficult than doing it with just one screen. That's just me though :)