A laptop with a Centrino chip instead of Pentium uses less power as it is designed for laptops, so increases battery life and requires a far smaller power adaptor to run.
I have had a number of different brands over the years, never had any trouble with any of them, and all have been pretty similar, so I dont think there is a huge difference in brands. My latest is an Asus. I love it. They are the company that builds the laptops for Sony and Apple, and it is very well built. It was by far the best value for money i could find at the time.
I also have a work laptop which is a low end Toshiba. The build quality is shocking, though Toshiba do have some good high end models. It is worth shaking the screen etc when buying a laptop to see how well built it is compared to others, as laptops get a lot of wear and tear. The screen costs almost as much to replace as buying a new machine so make sure it is sturdy.