I wouldn't look at it like that, both are pretty demanding. From the perspective of someone who used to be a GM and Squid at the same time, it looks like this:
Hosting team requires more of your team in one sitting - tourneys often take more than an hour, other in-game events can be even longer. Working with events means you're expected to be creative and reliable when it comes keeping deadlines, preparing those events and whatnot. By its nature, it's also more of a team job, you cooperate with other team members almost constantly. Currently, the job is relatively easier than it used to be as responsibilites such as server sitting, in-game moderation, solving general reports and hard hosting quotas were removed.
With Market Squad, you have a bit more freedom of choice as to when do certain parts of your job - you can jump in, solve a report or two, jump out, rinse and repeat few times a day. Most of the cases you solve yourself (as a full, trials, as mentioned before, are being supervised), asking for input when the case is pretty complicated or involves other reports, that are currently being handled by other Squids. Team communication focuses on those instances, as well as discussing rules and changes to them if needed. Still, some reports are demanding and consume quite a bit of your time, as you often need to investigate alt accounts, transaction logs, exchange PMs with involved parties, write TSA actions (this part is a pain in the ass when you got yourself a case with a lot of items to transfer) and so on. I'd say that, as it is currently, Squid's job is more responsible, as in, it's up to you (mostly) whether someone will get their items back, whether the scammer is punished and for how long. Any mistakes done by a MS generate bigger issues than ES's.
It's all a matter of preference, pick your poison.