I wish it wasn't named VX Ace, so people would stop assuming its just "an upgrade" of vx.
Seriously, if you remove the whole RTP style thing (which jesus guys you can make different style tiles/sprites), the difference between VX and Ace is just as large if not larger than XP to VX. If Ace is "Just an Upgrade of VX" then VX is "Just an Upgrade of XP".
Seriously, ignore the graphics format. Forget that one thing. And examine everything else. And you will see exactly what I'm saying. And let's be honest here, in the grand total of the entire program, the graphics formats are A REALLY SMALL THING. And keeping the graphics format was so that everyone had huge backlogs of fan made graphical materials to work with.
The ONLY thing XP has going for it over Ace is the maps. And if you know what you are doing in Ace, that is not a problem at all. The idea that XP needs an "upgrade" (which isn't even what Ace WAS) is really just not true.
Ahem, Mr. Touch, but I severely disagree with you in this point... I already used RPG Maker 2000/2003/XP/VX and now Ace. Specially 2003 and VX, and even excluding the Graphics I consider Ace to be something like an upgrade and not an entirely new RPG Maker. I generally compare this case with RPG Maker 2000/2003, the idea behind is basically the same for me.
Why? I already stated it's not exactly the Graphics. The name, maybe? No! There are a lot of factors, just to say some: The map editor and most of the interface is almost the same! It's a pure plain copy (aka revamped interface). The color scheme (a bit greyish this time), the organization of tilesets ...Everything!
Most of the default engine too, there are plenty of optional features like TP, caterpillar, etc, everything can be turned off or not used and... Poof! We have a perfect VX-like game! The compatibility in engine shows it too, I made VX to work with RGSS3 with almost no problems! The screen resolution too... OMG! I could stay in this chair hours and hours to say what's equal...
Everything is so similar, the name and Graphics are only consequence of this! Well, this time Enterbrain did a good job and updated some resources and the RTP is more complete than VX. More tileset graphics, musics in OGG, upgraded System graphical resources (Balloons, Iconset,...) and et cetera. See, an upgraded RTP was included on Ace.
And what's different from VX? Well, a different Ruby version (Hmm, an upgraded one!) Some generators here and there, some notable features like "Sets of Tilesets" and Traits, and everything else that is different but unnoticeable. I have sufficient reasons to guess it's an upgrade and I really think it's better to think this way, to prevent disappointments with its limitations.
Well, this discussion is unproductive, being or not an upgrade doesn't matter at all. But I said what I thought. VX can be said as an upgraded XP (with similar reasons I used), but I don’t like to see that way. Enterbrain did an excellent job recently, I say this all the time. But it's an upgraded VX, and many people here would still prefer an upgraded XP (Not exactly me, lol).