It's all about the kilowatts.! I looked at spec sheets for various Thermasol and MrSteam units. Looks about the same to me. I saw some MrSteam units calling for 49+ amps. So the comparison between any of the units is of course the approximate room size, but also the amount of steam and how fast it steams up. Thermasol advertizes "steam in seconds,not minutes"
So to make your choice, you need to line up the detail spec sheets for the various models and compare features.