I have the Gripzilla- and am also evaluating the Mous Limitless 5 and the Phone Rebel. And to be honest- I'm finding it difficult to justify the other cases. The Smartsh Gripzilla is very grippy on the sides and back, feels good in the hand, has a tight case fit, excellent MagSafe attraction and seems to be quite protective. It is also relatively inexpensive. It lacks features like "air shock," and is heavier/slightly bulkier than the Mous and Phone Rebel cases. However, while I haven't tried out the Limitless 5, some reviewers feel it is still slippery overall, even with the indentations on the side. It also seems to have uneven quality control. As for the Phone Rebel- its USB C cutout is reported to be too small for some USB C cables, and I am not sure I like the like the decreased lip around the left/right sides of the phone screen- supposedly compensated for by the raised four corners. I am also not sold on the metal protection around the camera housing- it seems it might be damaged easily (though replaceable).
I’ve never tried smartish cases but the gripmunk looks more my style. Def seems like great value for the money. I’ve recommended for some friends in the past.