if you need the performance, a 15inch will typically be able to house higher performaing parts, and is a little cheaper for a similar config, but it all depends on you. i have a 15inch acer aspire 5920, it is a little on the bigger side, but i dont mind it too much. if you use the laptop on the go more often, then the 13inch might be better, if it is used more at home or as a main computer, then getting the 15inch would be more benficial. if you decide to get a 15inch dell, make sure it is the xps1530 and not the inspiron if graphics performance is important as the xps uses the gddr3 version of the 8600m gt, while the inspiron only has the crippled gddr2 version. EDIT: its also much sexier than the inspiron imo too.