Unlimited wireless plans have become the default. Gone are the days when consumers paid for an allotment of minutes, texts, and data. Plans like that still exist, but they're not the norm for customers of the big four carriers: AT&T (NYSE:T), Verizon (NYSE:VZ), T-Mobile US (NASDAQ:TMUS), and Sprint (NYSE:S).

Of course, history has shown us that nothing is simple when it comes to wireless carriers. "Unlimited" is a term that's open to interpretation. Think of carriers as an all-you-can-eat buffet where customers pay extra for crab legs or access to the hibachi bar. Your unlimited plan may include slower data, slowdowns at peak times, or a limited ability to use your phone as a mobile hotspot. In all cases, the carriers reserve the right to slow down data for their heaviest users on the lowest-level "unlimited" plans.

Comparing unlimited plans isn't apples to oranges, but it's sometimes apples to really different-looking apples. This is a clear case of consumers needing to pay attention to what they're purchasing so they actually get the features they think they're buying.

A person with thumbs poised above a smartphone

"Unlimited" has become standard, but its definition varies. Image source: Getty Images.

What does each carrier offer?

For purposes of comparison, we're going to look at the cheapest unlimited plan offered by each carrier. Differences will be noted, and we'll try to explain how each company defines "unlimited" when it comes to its cheapest plan. All plans, unless otherwise noted, require that customers opt for autopay. In addition, we're looking at plans that do not include special offers tied to buying or trading-in certain phones.

Verizon: The company's "Go Unlimited" plan offers DVD- rather than HD-quality streaming. It also has its wireless hotspot speeds capped at 600 kilobits per second (Kbps), but faster 4G service on higher-priced plans. For this plan, Verizon charges $75 for one line, $130 for two, $150 for three, and $160 for four.

AT&T: Called "Unlimited & More," AT&T's plan offers a lot of perks, including 30 channels of live television and thousands of hours of on-demand shows; its video is DVD-quality. But this plan has no mobile hotspot data. Consumers pay $70 for one line, $125 for two, $145 for three, and $160 for four.

T-Mobile: It's important to note that T-Mobile prices are functionally lower than they appear. It's also relevant to point out the T-Mobile is awaiting regulatory approval on its deal to purchase Sprint. T-Mobile charges $70 for one line, $120 for two, $140 for three, and $160 for four. It throws in paying for your Netflix subscription once you hit two lines, and all plans include mobile hotspots with up to 4G speeds, as well as DVD-quality streaming.

Sprint: The No. 4 carrier has been the most aggressive. Its current "Unlimited Basic" deal offers 500MB in mobile hotspot use as well as DVD-quality video streaming. It also offers a free Hulu subscription. Plans start at $60 for one line, rising to $100 for two, $120 for three, and $140 for four.

Carrier 1 line 2 lines 3 lines 4 lines
Verizon $75 $130 $150 $160
AT&T $70 $125 $145 $160
T-Mobile US $70 $120 $140 $160
Sprint $60 $100 $120 $140

Data source: Verizon, AT&T, T-Mobile US, and Sprint. Table by author.

Which is the best deal?

As you can see above, pricing is fairly similar, but what counts as "unlimited" varies quite a bit. On a pure pricing basis, Sprint is the cheapest, and it offers the addition of Hulu, but its mobile hotspot data offering is very limited. It's also worth noting that over roughly the past year, Sprint has been the most aggressive in offering limited-time discounts on its already low prices.

T-Mobile may actually have the best value when you factor in that its prices include all taxes and fees, as well as unlimited mobile hotspot use. That gives the "Un-carrier" an edge among consumers looking for both price certainty and freedom from worry about the limitations of their "unlimited" plans.

Daniel B. Kline has no position in any of the stocks mentioned. The Motley Fool owns shares of and recommends Netflix. The Motley Fool recommends T-Mobile US. The Motley Fool has a disclosure policy.