Even after rising 7% since I called Apple (NASDAQ:AAPL) my top stock to buy in 2018 earlier this year, I still think Apple shares offer investors a compelling risk-reward profile.

Call me biased. After all, you'd probably be right: I've owned Apple stock for years -- and I have no plans to sell. But I'm biased for a reason. For the most part, Apple's performance over the last 10 years in relation to its valuation has consistently left the stock looking attractive. This remains true today, with Apple trading at just 18 times earnings despite its accelerating revenue and recent earnings-per-share growth.

Apple Store in Upper West Side New York City

Apple Store. Image source: Apple.

Here are two reasons I'm betting Apple will continue to outperform the market.

The Street underestimates the value of Apple's platform

Every Apple product sold gives customers access to the company's ever-growing and highly integrated ecosystem of hardware, software, and services, or Apple's platform. There was a time when customers' primary interaction with Apple was through software and applications on Mac computers. But now, Apple customers are increasingly entrenched in Apple's ecosystem through not only a range of Apple products, such as the iPhone, iPad, Apple Watch, and AirPods, but also through an increasing number of services, like Apple Music, Apple Pay, and third-party services available in the iOS App Store.

A good example of one area where Apple is benefiting handsomely from the platform its customers have access to is in the growth of paid subscriptions from Apple services and third-party services available in the App Store. Subscriptions surpassed 270 million in Apple's most recent quarter -- up 30 million sequentially and 100 million compared to the year-ago period. 

Of course, Apple's strong growth in its overall services revenue is arguably the best representation of the momentum Apple is seeing from monetizing its platform. Apple's services revenue was up 31% year over year in the company's most recent quarter. As Apple's second-largest segment after iPhone, services revenue accounted for 15% of total revenue during the quarter.

During Apple's earnings call for its first quarter of fiscal 2018, management said its active installed base, or the number of its devices that are being actively used, swelled to 1.3 billion -- up 30% in just two years. And in Apple's most recent conference call, management noted that its active installed base is "growing at a double-digit number on a year-over-year basis."

Apple CEO Tim Cook is clearly optimistic about the opportunity for the tech company to better monetize its growing user base. "[W]ith that kind of change in the installed base and with the services that we have now and others that we are working on," Cook explained, "I think this is just a huge opportunity for us and feel very good about the track that we're on."

New products will drive revenue growth

While Apple's HomePod doesn't appear to have been a blockbuster hit with customers, investors shouldn't underestimate how well Apple can launch new, premium-priced products at scale.

AirPods laying on an iPhone

AirPods and an iPhone. Image source: Apple.

The Apple Watch and Apple's more recently launched AirPods have been driving significant growth in Apple's other products segment. In Apple's most recent quarter, other products revenue was up 38% year over year. Apple's wearables business, which includes sales of Apple Watch, AirPods, and Beats products, was the primary driver of this growth, management explained in the company's second-quarter earnings call. Wearables revenue was up 50% year over year in the first quarter.

With such rapid growth from its other products segment, Apple certainly won't stand idly by and bask in its reinvigorated iPhone revenue growth. Indeed, Apple is expected to be working on several new Apple-branded headphones and a new version of the Apple Watch to be launched between late this year and sometime next year.

Even if investors want to refrain from relying too much on a rosy outlook for Apple's services and other products segments, the company's recent performance alone easily justifies the tech company's valuation. Apple's year-over-year revenue growth rate has accelerated every quarter since it returned to growth in the first quarter of fiscal 2017 -- and second-quarter revenue and earnings per share increased 16% and 30%, respectively, compared to the year-ago quarter.

Of course, there's always a risk that these catalysts don't pan out to be meaningful growth drivers, or -- even worse -- iPhones lose their luster with customers, and Apple fails to make up for the maturing product in other areas. Still, Apple's conservative valuation and its long track record of continually pleasing customers suggest it's unlikely the company won't be able to keep growing revenue and earnings per share over the long haul.