Sony's (NYSE:SNE) stock price has soared over 60% in the past year, as most of its operating segments posted solid sales growth.

Management has done a good job keeping a lid on operating costs, especially in shedding underperforming assets in its semiconductors segment. As a result, the company is expected to grow operating income 149% year over year for fiscal 2017 (ending March 31).

Sony's Playstation game console

Playstation 4 game console. IMAGE SOURCE: SONY. 

But while gaming and music are very attractive businesses that offer long-term growth and expanding profit margins, most of Sony's segments have struggled year after year. This poses a significant challenge for investors who may be thinking about taking a long-term position in the company.

The gold rush from digital distribution

Sony operates business segments that span financial services, semiconductors, and of course, home electronics. However, the strongest ones are gaming and music where digital distribution trends in these respective industries are driving steady sales growth and healthy margins.

Demand for digital music streaming services and robust sales of the Fate Grand Order mobile game have been a good combination for Sony's music segment, which is expected to increase sales 20% to 780 billion yen ($6.9 billion) year over year in fiscal 2017.

Metric Fiscal Year:
2012 2013 2014 2015 2016 2017*
Music sales

441.7

517.0

560.4

619.2

647.7

780.0

Music operating income

37.2

52.4

58.2

86.5

75.8

110.0

Total sales

6,795.5

7,767.3

8,215.9

8,105.7

7,603.3

8,500.0

Total operating income

226.5

26.5

68.5

294.2

288.7

720.0

Dollar values in billions of Japanese yen. Data source: S&P Capital IQ. *2017 data is based on management's guidance.

And Sony's gaming segment has consistently outperformed since the Playstation 4 (PS4) launched in 2013. The PS4 has sold 73.6 million units through Dec. 2017, dominating the current console cycle over Microsoft's Xbox One.

The PS4's growing installed base provides the company with a very profitable digital distribution platform. Gamers download games directly to their console, and Sony gets a cut of every sale. There's also the Playstation Plus monthly subscription which has 31.5 million members -- this acts as a recurring revenue stream for the company.

Based on management's guidance, sales for Sony's gaming segment are expected to increase 18% to 1,940 billion yen ($17.2 billion) year over year in fiscal 2017.

Metric Fiscal Year:
2012 2013 2014 2015 2016 *2017
Gaming sales

749.9

1,043.9

1,388.0

1,551.9

1,649.8

1,940.0

Gaming operating income

(3.7)

(18.8)

48.1

88.7

135.6

180.0

Amounts in billion yen. Data source: S&P Capital IQ. *2017 numbers based on management's guidance.

As you can see in the above tables, the gaming and music segments have seen operating income grow faster than sales due to the consumer shift from packaged goods to digitally delivered content.

Upside in self-driving cars and robotics

A second reason is potential long term upside in self-driving cars and other high-tech products Sony has in development. At the 2018 Consumer Electronics Show, Sony unveiled its plans for the self-driving car market with its image sensor products. The company is also working on bringing robotics and artificial intelligence to its video and audio technologies in consumer electronics.

These high-tech initiatives provide investors optionality for long-term upside. For example, while success in self-driving cars is not critical for Sony to be a good investment, success in that area could generate additional opportunities that may not be reflected in the stock's current valuation.

With that in mind, Sony is not an expensive stock with a relatively low forward P/E ratio of 16x. That's lower than the forward P/E of 18x for the average stock in the S&P 500.

Digital trends in the gaming and music segments, plus the opportunity in hyper-growth areas are two reasons to buy Sony. However, gaming and music make up only 32% of Sony's expected total sales for the current fiscal year. When you buy a share of Sony, you're investing in other business segments, many of which you might not want in your retirement account.

Clouding the investment case

Sony's other segments, such as pictures and home entertainment have had a strong year due to the release of Jumanji: Welcome to the Jungle, season 2 of the hit TV show The Crown, and an upgrade cycle for 4K TVs. But Sony has been involved with these segments for a long time, and they've never been able to generate consistent, long-term growth. In fact, Sony hasn't grown its revenue much at all over the last 15 years.

There's also Sony's financial services segment, which includes a life insurance and bank business in Japan. This segment has been stable (with low growth), and it adds risk to Sony's balance sheet. For example, Sony's equity-to-asset ratio is only 17.7% as of Dec. 2017, which is not much higher than a big bank.

And therein lies the dilemma. Sony is a mixed bag of businesses, and for many investors, the weaker segments end up overshadowing the opportunities in music and gaming.

And that's one major reason to stay away.

Teresa Kersten is an employee of LinkedIn and is a member of The Motley Fool's board of directors. LinkedIn is owned by Microsoft. John Ballard has no position in any of the stocks mentioned. The Motley Fool has no position in any of the stocks mentioned. The Motley Fool has a disclosure policy.