I use RMXP because of the number of colours, and for short games I use RM2k, who is the same as 2k3 but whit more patches (mp3 sounds, key, mouse).
Also, I started to use MMF 1.5 and 2.0, and this software ROCKS!! Too bad for the mapping system that requires drag and dropping an element, but it's better than RM for every type of game except an RPG. Anyway, I use RMXP for my main project -> it's an humouristic adventure game, but it's gonna be hard to make the pixel-based a-rpg combat system for the a-rpg fighting sequences.