Less, colors, but not lower resolution. It is the VGA graphics converted to 640x200 in 16 colors with a lot of dithering in real-time, taking some CPU time. Not a big deal on modern computers, but it is usually quite noticeable on the intended platform, which would be an old PC without VGA compatibility, and most likely not a very fast CPU either.
Imho, Monkey Island is the only game worth seeking the EGA version after playing the VGA version. That game has some noteworthy differences affecting the overall style. I like both equally.
But keep in mind, if you’re seeking the Amiga version. Unlike Indy3 the it is not entire based on the EGA version. It is a mix of the EGA actors and converted VGA scenery to 32 colors. Oddly enough, some Amiga versions use accurate EGA colors, while some other versions use the altered palette like in earlier SCUMM games, ie. with brighter pink etc., ie. it is either luminescent Guybrush or sunburn Guybrush. The latter better fits all those night scenes, imho.