"They both have a niche, but the AMD laptop I linked to will destroy that one in performance, which is more important than size and battery life to most gamers."
Why would a gamer shell out over $3000 for a laptop when he could get better performance at half the price with a desktop model? Just what does portability mean to a hard-core gamer? They are usually introverts that don't make it out of their room for days at a time.
You confuse the reason why people buy laptops with your need to justify an AMD64 laptop. Maybe if you think long and hard you'll discover why the Centrino/Pentium M CPUs are having a runaway success in the laptop/portable arena.