Shares of Chinese social network Weibo (NASDAQ:WB) have surged 185% this year, fueled by five straight quarters of accelerating year-over-year sales growth. Wall Street expects the company's revenue and non-GAAP earnings to respectively soar 72% and 110% this year -- compared to 37% sales growth and 167% earnings growth in 2016.

I've previously stated that Weibo is still a good growth play for speculative investors. But I also know that its trailing P/E of 99 will likely spook risk-averse investors. So today, I'll discuss a relatively "safer" way to invest in Weibo through its former parent company, SINA (NASDAQ:SINA).

Weibo's mobile app.

Weibo's mobile app. Image source: Google Play.

Understanding the relationship between SINA and Weibo

SINA, one of China's oldest internet companies, hosts a network of news portals and apps. In 2014, it spun off its microblogging site Weibo -- often called "China's Twitter" -- in an IPO. SINA retained more than 50% ownership in Weibo, and Alibaba (NYSE:BABA) was the new company's second largest shareholder.

SINA gradually reduced its stake in Weibo to 46% (with 72% voting power) with two share distributions, each of which gave SINA shareholders a single share of Weibo for every ten shares of SINA they held. Therefore, an investor who originally owned 100 shares of SINA would now own 20 extra shares of Weibo.

SINA did this to address the concern that Weibo, which was free from SINA's slower-growth portal business, was outperforming its former parent company. That was certainly true this year, with Weibo's 185% rally crushing SINA's 75% growth. Meanwhile, Alibaba boosted its stake in Weibo to 31.5% late last year.

Comparing the growth figures

SINA's growth figures can't match Weibo's, but they're still very strong. Analysts expect its revenue and non-GAAP earnings to respectively grow 52% and 101% this year, compared to just 17% sales growth and 94% earnings growth in 2016.

SINA's mobile app.

SINA's mobile app. Image source: Google Play.

72% of SINA's revenues came from Weibo last quarter. That part of the business posted 81% year-over-year sales growth as both advertising and non-advertising (valued-added services like virtual gifts) revenues jumped. Weibo's monthly active users (MAUs) rose 27% annually to 376 million during the quarter.

However, revenues at SINA's portal business rose "just" 26% annually and accounted for the remainder of its top line. That growth is impressive for a nearly 19-year-old network of online portals, but it still reduces SINA's total sales growth.

So why shouldn't investors just buy Weibo?

Weibo is a better growth play than SINA, but three things arguably make SINA the safer stock to own. First, SINA trades at just 61 times earnings, and its forward P/E of 29 looks much cheaper than Weibo's forward multiple of 44.

Second, the valuation gap reveals that SINA, which has an enterprise value of $5.5 billion, owns a 46% stake in Weibo, which has an enterprise value of $23.4 billion. The simple math tells us that if the market valued SINA's stake in Weibo on a similar level as its stand-alone stock, its stock should be trading at much higher levels. That's why SINA -- not Weibo -- was the target of a recent activist move.

Lastly, Weibo has frequently been mentioned as a potential takeover target for Alibaba, since it already owns a large percentage of the company. An acquisition would generate a lot of cash for SINA, which could be used on buybacks, dividends, or other acquisitions. But since SINA has a lower enterprise value, it might be smarter for a suitor to simply buy SINA to gain control over Weibo. Either outcome would generate big gains for SINA's investors.

The bottom line

If you've been following Weibo but have been reluctant to pull the trigger on such a richly valued stock, it might make sense to buy SINA instead. SINA might underperform Weibo over the next few quarters, but its lower valuation could reduce its downside potential during a major market downturn.