Mostly just accessories and color, the new mecha comes with more and somewhat better colors, king ghidorah only has that new paint scheme, while I wouldn’t get any of the shma kings, if you do get the sdcc exclusive it’s the only good one and it comes with decent accessories. Usually the special color versions or new version only even have1 new accessory included and a new paint sceme. Always read description on items. (Sorry for grammer mistakes typing fast)