I have a preference for BOINC as well but the only place that BOINC clearly has an advantage (at least as far as I am aware) is on machines that have multiple processors or dual core processors and a little bit of an advantage on a "Hyper-Threading" Pentium 4.

On multiple processor and dual core machines, BOINC is clearly superior in that it allows you to run multiple work units in about the same wall clock time as you can run one assuming you have adequate memory and disk space. On HT machines, you can run two and get some work out of the HT so it goes a touch faster again assuming you have adequate memory and disk space. (Double the memory requiremets that adywebb point you to if you run 2 WUs.)

But, if you have a single core P4 without HT or a single core AMD, then the case for BOINC needs to be made on the other benefits of BOINC; like caching of work units etc.

This Thread discusses this more. Good luck with your new computer, and your choice of agent (you can't go wrong) ... and Thank You for contributing to the cause.