In some ways, Sprint (NYSE:S) and Frontier Communications (NASDAQ:FTR) are in very similar predicaments. Both face larger, more successful rivals in the battle for customers, and both have struggled to gain (or in Frontier's case, not lose) market share.

The difference -- and it's a big one -- is that Sprint has a way out. It has agreed to be acquired by T-Mobile US (NASDAQ:TMUS) in a deal that would give the combined company the resources needed to compete in the wireless space. Frontier has no similar white knight, so its fortunes rest in its own ability to right its sinking ship.

A person holds a smartphone.

Sprint is merging with T-Mobile to become a strong No. 3 in wireless. Image source: Getty Images.

The big Sprint fear

If you assume that the T-Mobile deal will go through, then Sprint is a better stock buy than Frontier. The acquisition will happen at "a fixed exchange ratio of 0.10256 T-Mobile shares for each Sprint share or the equivalent of 9.75 Sprint shares for each T-Mobile US share," according to a press release.

Since Sprint shares have fallen and T-Mobile shares have gone up since the deal was announced, even buying in now will pay you a premium. The caveat is that there's no guarantee federal regulators will approve the deal. If it gets shot down, Sprint will have to go it on its own or find another buyer -- something it's failed to do in the past. A denial of the deal would likely send Sprint stock tumbling, and the company's future would become murky at best.

Can Frontier turn around?

Frontier has lost subscribers in every quarter since it spent $10.54 billion in April 2016 buying Verizon's wireless business in California, Texas, and Florida. That deal did give the company critical mass it needed in order to cut $1 billion in expenses, but that edge is slowly dribbling away as customer loss continues.

Despite the continued losses of both customers and cash, CEO Dan McCarthy has steadily promised that things are going according to plan. In every quarter since the deal, he has maintained that subscriber trends will eventually move in a positive direction.

"We continued to make further progress in the second quarter with the key initiatives that we have underway across the company," he said in the second-quarter earnings release. "We are pleased to have maintained good subscriber momentum despite facing typical second-quarter seasonal headwinds. Underlying trends should continue improving in the latter half of this year, once summer seasonality is behind us."

Give McCarthy credit for seeing positive trends in what has been a two-year-plus slide. Losses have slowed, but the company has also shrunk considerably.

Which is a better buy?

Sprint is a better buy because it seems likely that while there may be concessions made, its deal with T-Mobile will be approved. That will give shareholders shares in a combined company with strong leadership (T-Mobile's management team) and the money and bandwidth assets it needs to compete.

Frontier has a ways to go before it's even clear if the company will survive. It has managed its cash and borrowing well, but it's in a competitive space -- internet and broadband -- with no real competitive advantages. It might be cheaper than some big cable rivals, but it's not cheaper than digital cable or cutting the cord.

Sprint is the best of a bad lot here. Ideally, you would buy neither of these stocks, because the upside of getting a small deal with a T-Mobile acquisition is outweighed by the risk of the deal not being allowed.