The stories of companies not optimizing their code for AMD processors are BS. Don't get Intel for that reason. The code might not be optimized, but that doesn't make all that much of a difference. And if you want a gaming PC, Athlon 64's eat the P4 alive for gaming. Or did you miss that memo?
I have a P4 in my computer, but only for cost and features of the components surrounding the CPU itself. In particular, the motherboard. I got the ABIT BH7, which is an awesome motherboard designed for overclocking and has a minimalistic feature set with everything I want - SATA, USB 2.0, no old technology junk like serial ports and the such, and the thing costs only $90. If I wanted a similar quality motherboard with SATA, I would have to pay about $130 for a motherboard if I got an AMD CPU.
That's an example of good reasoning behind buying a CPU. The CPUs are so close it doesn't really make a difference which CPU you go for, unless you're aiming for the high-end, in which case the Athlon FX eats any P4 alive.
Wich that said, I suggest you, for your own good, do research. That P4 2.53 GHz is a rip-off at $140. You can get Athlon's much faster than that for $50 less.
EDIT: oops, missed that it's a CPU/motherboard bundle. Still, check out that motherboard. It looks really cheap. It won't hold up to much, just so you're aware...