Yes, the XP laptop by a long shot. Both run the same Antivirus and antispyware programs. The desktop is drastically faster in terms of hardware, but Vista has so many bells and whistles that it drags a bit on boot.
Once running, it seems to be plenty quick though.
Vista is very bloated. Even on hot hardware, it runs slowly. Imagine buying a hot new laptop and it runs worse than your four year old desktop - thanks Vista.
The latest service pack for XP actually results in an increase in operational speed.