As a user of Rm2k3, I would say use RMXP.
The reason i chose to use Rm2k3 is because I have years of experience with it. I tried RmXP, but it took way too long to do what I wanted it to do. To do anyhting as efficently as Rm2k3 you would have to learn ruby, it was more flexable, but would take me longer to do stuff.
If you're starting off fresh RMXP is probably a better choice. be prepared to learn Ruby though, or you won't get too far.
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