Nah, discuss the...erm...fact that XP is supposed to be the better engine, yet RM2K3 outclasses it full stop.
The DEFAULT engine outclasses it full stop. Custom engines have yet to make a major impression on people, besides the side view battle system that's included by default in RPG Maker 2003 anyway.
But yeah, I'm debating whether or not to make a full list of the differences between RPG Maker 2003 / XP's default engines.