Using 9600 editor for 9400 configs does have benefits.

You can put widgets such as menus or things that will be show with Prontoscript outside of the visible area (240x320 top-left region) such that you can do page layout with extra widgets without so much clutter (don't have to keep moving things around).

Also, if you are building a resource page, you can use the extra space to house panel widgets (with image resources). You can usually layout more widgets on a 640x480 page than you can on a 240x320 page.