There are several factors to consider when aiming to whittle down the choice of the best mobile hotspots to just one.
First, consider the reasons behind your interest. If security is a big concern - and with public Wi-Fi hotspots not usually secure and often unreliable, it certainly should be - then you might want to consider mobile hotspots that offer robust security features or additional ethernet ports. Speed should also be a consideration, and you might wish to purchase a hotspot that is 5G compatible when this becomes more prevalent.
Lastly, consider how many users the hotspot will have. If it's just you, you'll have a pick of the lot, but if you're in a business with upwards of ten users, you'll have a more limited selection.