For about a month, Chinese consumers waiting for the iPhone 6 to debut in their country have been resorting to the gray market, paying steep markups for Apple smartphones bought abroad.

With regulatory hurdles cleared at last, the phone went on sale Friday in the mainland. And while consumers in some other markets waited in long lines to buy the phone (along with Chinese scalpers planning to smuggle it back home), in Shanghai the queues were quite manageable. Only people who had preregistered could pick up a smartphone.

Western products are often more expensive in China because of taxes or markups, and the new iPhone is no exception. The most inexpensive model sells for $863 at the China Apple Store, versus $649 for a contract-less model in the U.S.

For Apple, keeping Chinese fans happy is key: Greater China, including Hong Kong and Taiwan, accounted for 16% of sales in the most recent quarter. The iPhone 6 launched in Hong Kong on Sept. 19.

Giants like Apple and Samsung face increasing competition from fast-growing Chinese smartphone makers Xiaomi, Huawei and Lenovo, which sell high-quality phones at lower prices. (Four-year-old upstart Xiaomi was the No. 1 smartphone vendor in China in the second quarter, according to data from Canalys, and Xiaomi's international marketing director, Amanda Chen, is one of Ad Age's 2014 Women to Watch China).

So what makes people stick with Apple? As the iPhone 6 launched, Ad Age visited an Apple Store in Shanghai--one of 12 in mainland China--to chat with the brand's most loyal Chinese customers.

Name: Zhang Jian Ping

Age: 55

Occupation: Retired bank employee

Favorite brands besides Apple: Lancome, though she says: "I'm lazy when it comes to using beauty products. I'm not lazy about technology."

Tech-savvy Ms. Zhang bought an iPhone 6 for her sister. She's an Apple fan too, and an avid user of WeChat, the hot Chinese social app.

Ms. Zhang lost her own iPhone 5S a month ago and tried to get by with a borrowed Android phone while waiting for the new Apple model to come out. "But it was terrible, I hated it," she said. "I'm very brand loyal." She ended up buying an iPhone 5C to tide her over, and now she wants to upgrade to the iPhone 6 Plus. Her son was concerned that it might be hard to hold and handle, but she tried it out in the store and liked it. She's already got an iPad for watching videos, so she's not sure why the larger smartphone screen attracts her. "It just seems cool."

Name: Juice Qu

Age: 25

Occupation: Post-graduate student in materials engineering, and part-time entrepreneur (he sells tickets for K-pop events on e-commerce giant Alibaba's site Tmall.)

Favorite brands besides Apple: Nike and U.S. streetwear label SSUR.

Mr. Qu uses an iPhone for work contacts and a Xiaomi for friends. "The Xiaomi is also a very good phone," he said. Mr. Qu was charging his old iPhone using a stylish power bank from Xiaomi (it can recharge an Apple iPhone 5 about 4 1/2 times in one go and costs only about $11.)

Name: Angela Zhou

Age: 25

Occupation: Planning the production process for a German automaker

Favorite brands besides Apple: Chanel lipstick, and Chanel, Gucci and Dior for perfume.

Ms. Zhou sped up to the mall on the back of her father's moped. She opted for the iPhone 6 in gold, a sought-after color for Chinese consumers. She also had a gold case on her old iPhone 4, which she said has been slow since she upgraded to iOS 7. With the rise of Chinese brands, why does she stick with Apple? For its functionality and design: "There are some good choices, but Apple is a better choice."

Name: Alexander Shen

Age: 20

Occupation: Student in hotel management

Favorite brands besides Apple: Uniqlo

Mr. Shen's iPhone 5S broke down a week ago. While waiting for the new model to come out, he was phone-less for a week, getting by with a friend's iPad Mini. He opted for the big-screen iPhone 6 Plus: He's a fan of Japanese animation and often watches videos on his smartphone. Why does he remain an Apple fan? "Apple changed people's lives."