If you're willing to sacrifice internet speed in exchange for unlimited hotspot data, you should consider Visible's $40 Unlimited Plan. Visible's plan offers unlimited 5 Mbps data and reliable coverage, and it's about half the cost of both AT&T's and Verizon's plans. But you won't be able to stream or game at such a slow speed.
If reliable coverage matters most to you, then Verizon's Do More Unlimited is your best bet. But it's not a great deal considering Verizon's plan gives you only half the data as AT&T's but at almost the same price.
If you want lots of high-speed hotspot data and are willing to pay for it, AT&T's Unlimited Elite is the plan for you.