Utility stocks are a haven for investors seeking reliable dividend income. Utilities became known as “widow and orphan” stocks, meaning they were extremely safe investments.

Southern Company (SO) is a very high-quality utility dividend stock. It is a Dividend Achiever, a group of 265 stocks with 10+ years of consecutive dividend increases.

Meanwhile, Exelon (EXC) is also a dividend-paying utility. It has a solid 3.7% dividend yield, and the company recently raised its dividend.

Southern and Exelon look like similar stocks—but looks can be deceiving. Utility stocks are not all created equal. This article will discuss three reasons why income investors should prefer Southern to Exelon.

Reason #1: Business Model

The biggest difference between Southern and Exelon is their business models. Even though they are both utilities, they have very different operations. Southern has positioned itself well, given the changing energy landscape in the U.S. It has gradually moved away from coal, and has steered its generation assets toward natural gas. The boom in domestic natural gas production has resulted in falling natural gas prices.

As a result, Southern’s energy mix is as follows:

Southern’s reported earnings-per-share dipped 1% in 2016. The company earned $2.57 per share, which more than covers its current annualized dividend. Revenue rose 14% for 2016.

Exelon is the largest operator of nuclear fleets in the U.S., with 23 nuclear reactors.

Nuclear energy makes up nearly two-thirds of Exelon’s energy mix:

The economics of nuclear energy are challenging. Southern has benefited from a fairly low level of exposure to nuclear. In recent years, Exelon invested to build its unregulated operations. Competitive businesses now represent more than half the company’s total annual revenue.