In terms of computer brands, it all depends on what you want or value most in the purchase. In terms of insurance against hardware failures or catastrophic events taking place, the ITS Help Desk has been very pleased with Dell's service plans. Macintosh laptops have grown in versatility to the point that you can have both Mac OS X installed and Microsoft Windows, choosing which you would like to use at any given time and ultimately giving you the best of both worlds. There's quite a difference in pricing however in these two brands. I do see a lot of people with HP laptops who seem pleased with them. Ultimately, it's going to be a matter of what you think is right for you in terms of pricing and features.
We can however, be more helpful in terms of what you'll need for school. On our website we have a list of recommended specs for the computer you may wish to purchase, which is located here: http://www.sandiego.edu/its/helpdesk/kb/18725. We also advise having Microsoft Office 2007 (if you choose to have a laptop with the Windows operating system), rather than Microsoft Office 2003, as the majority of the campus will be moving on to 2007 next year.
If you have any additional questions, don't hesitate to call us at 619.260.7900, and anyone at the ITS Help Desk would be happy to assist you.