I'm personally not a fan of Core2 Duo CPUs. They seem a bit slow compared to both their predecessors and successors. (For me, I've oddly had better results on a single-core Pentium M @ 1.87 GHz than on a dual-core Core2 Duo @ 1.67 GHz.) If you want performance, of course, I would suggest the Inspiron. I'd also suggest trying out a store demo if you can. Laptop touchpads are hit-or-miss, and a lot of them aren't all that comfortable to use depending on the person. The same holds for the keyboard. Another thing a new computer will come with is a new battery instead of one that may not hold the greatest charge. Of course, you can always buy a new battery for the Precision.
I'd actually like to bring up a little psychological bit too. If you buy something yourself, you treat it better than if you received it as a gift. It'd probably last you a lot longer if you bought your own laptop.