As have may become apparent, personal opinion has a huge effect toward which one you use. Personally I don't like being limited, so RPMXP is my choice, you can do infinitely more with the scripting than events.
Why? Because the entire system in XP is PURE script. You don't have access to just common functions, you can rewrite ANYTHING. You could write the code to handle 16x16 sprites instead of 32x32 if you wanted, you could WRITE new functions for the event code, you can modify how the system handles damage, healing, you can write in new scenes (like different custom battles like Suikodens party and duel and large scale battles), you could, if you wanted, write the entire game system from scratch.
Of course, if you don't like programming RMXP is more limited unless you have access to pre-made resources by other people, which is what RMXP currently lacks. If more programmers wrote battle systems, or custom Scripts for it, and shared those, you would find that it's much easier to do what you want.
Also, there is efficiency, in 2003 to change the "battle formulas" you had to custom event ALL attacks. In XP you can go in and tweak the code, as an example: During one of my testing systems I changed the combat system to be % based, your weapon would have an attack value of, say, 200, meaning it would do 200 damage. To decide how much of that 200 damage a person could cause, you would take their STR and turn that into a %, ie. 50 STR = 50% of 200 = 100 damage. Same for magic and skills, a Fire spell would cause 120 damage, and with 82 INT you would do 82% of 120 damage. Then I changed it to be based on an exponent equation, so that 30 INT was like 50% and 120 INT was 105% and 200 INT was like 130%, meaning it paid well to keep your stats fairly even, and even maxing stats didn't provide a huge imbalance to the game.
Using that system I made enemies at the start of each battle recieve a "status" effect based on the average level of the party; these statuses reduced their stats by a %. So at level 5, an enemy would have 20% of their stats. In this way you just create all your enemies to be "end game" and you never have an uneven battle, since their stats will scale as your party scales. Keeps you from having to do all those horrible checks to make sure halfway through your team doesn't get overpowered or doesn't find encounters to be waaay too easy. You can easily mathematically reproduce ANY fight with a cheap calculator and 5 minutes.
I also added "shields" and "barriers" that could be "strengthened" by recasting them on your party members. These shields would wear down as enemies hit them, for example a spell would add 2 layers to your shield, cast it 5 times and you're at a cap of 10 layers to your shield, that would cause a reduction of 100%, and the enemy would "wear" the shield down when they hit it to 9 layers, which would cause the next attack to be 90% or some-such. Certain attacks could reduce shields much faster than others.
This was all done without slowing down combat, and without only 30 lines of changes and 20 lines of addition to the combat script. I didn't have to create dozens of events and long conditional nests, it also didn't cause a huge inefficiency because it was running a very poorly programmed combat system through lots and lots of events, which also required you custom script EACH attack.
Things such as that can be done easily through scripting, and barely at all through eventing. And that's just a low level, basic addition, there are many (many) thinks that eventing can NOT do that scripting can.
Another example? I'm currently working on making a battle system that's Active Time just like Chrono Trigger or FF7, etc, no, this feature wasn't included in RMXP by default, and to make it work I'll have to make threads to watch time and allow input seperate from the actual combat events, but I can program it however I want, OR I could program the whole system to work differently, this is something you basically will find impossible to do with just events, you cannot make 2003 emulate XP perfectly, but you COULD make XP emulate 2003 if you wanted to program it.
You couldn't really custom build a screen of menus like a buy/sell menu for upping the level of skills, like pouring special points earned in combat into making your Fire magic spells more powerful, or your Sword techniques harder to dodge, in 2003. You COULD simulate it, but it would be messy, not on it's own custom interface, and would again depend on an insanely huge custom designed combat system requiring your to Event script EVERY attack.
Steeper learning curve, but once you learn Ruby and how to change even the small things, it's about 500x more powerful than 2003.
Discord
Light Style