RGSS2, which is incorporated into RPG Maker VX, has a number of differences from RGSS1, which was included with RPG Maker XP. The main differences are listed below.

The default resolution has been changed from 640×480 to 544×416 and the default frame rate has been changed from 40 to 60. Smooth Mode has been removed.
Double buffering is now used for drawing in Full Screen mode. If your computer meets the recommended specifications, scrolling should be very smooth.
The function that would assume that the program had hung up if the screen had not been refreshed for a long period of time and automatically perform a force quit has been removed. Even if the screen is not refreshed, Windows messages will still be processed normally, so in most cases you can force quit by using Alt+F4 as usual.
It is now possible to easily perform a fade-in or fade-out of the screen. To do this, you use the Graphics.fadeout and Graphics.fadein methods.
It is now possible to get a bitmap image of the current game screen. To do this, you use the Graphics.snap_to_bitmap method.
The tilemap (Tilemap) class has been significantly changed to match the RPGVX map specifications.
It is now possible to use effects such as Blur or Radial Blur with bitmaps (Bitmap).
For sprites (Sprite), a wave effect (similar to a raster scroll effect) is now supported.
By placing font files in the Fonts folder inside the game folder, it is now possible to directly use fonts that are not installed on the system.
Shadow text is now supported for the Font class (Font). A number of the default values were also changed.
It is now possible to change viewport (Viewport) associations after the fact. Sprites and other elements associated with viewports will no longer be automatically freed.
The timing with which the BGM restarts after ME playback has been improved (Audio.me_play).
In addition to the above, a number of other minor changes have been made.