For physics specifically, I'd still take the HP-48 over a laptop, because there's no good PC software that provides a nice user interface for doing calculations with units. Undergrad physics (and to a lesser extent, chemistry) homework sets are much easier when your calculator is not only doing automatic unit conversions for you, but also type-checking those units throughout the whole process. The laptop only really becomes preferable when you're doing things like statistics or numerical integration where the sheer quantity of arithmetic becomes inconvenient for a handheld device.