Yeah I guess I would assume 'The Shimmer' is more formidable than 'The Zone.' There are quantified origins of the anomalies in 'The Zone' with all that 'noosphere' gobbledegook and the research opening a rift into it. And there was an ending where 'The Zone' was removed (even though it was retconned with the sequel) so I would feel that, though I don't know how, I would assume 'The Zone' is easier to deal with then 'The Shimmer.'
Plus you can still interact normally with The Zone in most respects. There's still physical laws and things working as expected in the most part with the exception of the notable anomalies. In 'The Shimmer' there's literally a magical shimmering barrier which surrounds the whole area and can mess with you, and than literally every other thing inside of that area is fucked up in some way. And there's no real theories beyond the extraterrestrial origin of 'The Shimmer' that can provide any insight into it that might eventually lead to workable countermeasures or strategies like there is with 'The Zone.' It's far less defined and thus less to work with.