If there were the best hardware wallet on the market, everyone would want to purchase it, making its producer a wealthy monopolistic asshole who would care neither about its customer nor their privacy and safety. Such a hardware wallet would unlikely be open-source either, which directly contradicts the principles of transparency, free competition, and decentralization inherent to the bitcoin ecosystem and bitcoin itself. Diversity and transparency are preferable when it comes to hardware wallets because it enables producers to improve their product gradually by sharing ideas, implementations, libraries, etc. Constant improvement of a product makes wallets safer and their users more satisfied. Not only is it good for customers themselves and their money, but also it facilitates the global adoption of bitcoin since it shows that the whole industry is mature enough to be part of the world economy.