Today: One analyst downgrades Apple (AAPL) shares on worries of tightening profit margins and weak growth, while another puts his faith in expected rollout of new gadgets, naming Apple the top large-cap stock. Also, Twitter continues its inexplicable surge.

A tale of two Apple analysts: One cautious, one bullish

It's a new year, but Apple is facing the same ol' questions, and analysts were split Thursday over Apple's fortunes in 2014.

Wells Fargo analyst Maynard Um downgraded Apple shares Thursday morning from "outperform" to "market perform," based on concerns about shrinking profit margins, limited growth and a swing in power from handset makers to mobile carriers.

While noting that "there was a lot to be positive about" in 2013, and pointing to expected launches of an iWatch, iBeacon and iPhone 6 this year, "we believe that in the iPhone 6 cycle, gross margins will come under pressure," Um wrote in a note. He also worried that Apple has little room to grow: "We see limited market opportunity absent material share gains or improvements in consumer spend(ing)." Furthermore, Um believes mobile carriers will begin to reduce the subsidy amounts for new phones -- now reportedly about $400 per iPhone -- which may discourage purchases from budget-minded consumers.

Still, Um maintained Apple's valuation range between $536 and $581 a share, which is right where it is now, closing Thursday at $553.13, down $7.89, or 1.41 percent.

On the positive side, later Thursday morning Brian White of Cantor Fitzgerald named Apple his company's top large-cap stock for 2014, pointing to innovative new products expected to hit the market and growing popularity in China.

"For 2014, we expect Apple to enter new product categories, re-accelerate growth in China and deepen its offerings in existing device categories," White wrote, citing the expected iWatch, new iPhones -- including a super-sized version -- and a 12.9-inch tablet/laptop hybrid "iPad Pro." White said such a device could be significantly cheaper than a comparable MacBook, since it would use Apple's native A-series processors instead of pricier Intel (INTC) CPUs.

White wrote that while 2013 was "a year to forget," Apple's holiday sales appeared strong and it's not facing supply shortages from its Asian factories, as it did last year at this time. Cantor targets Apple shares at a bullish $777. "After a challenging stock performance in 2013 . . . we estimate that Apple will return to growth in 2014, and we expect the stock price to reflect this improved performance," White wrote.

Markets start slow, but Twitter resumes its inexplicable surge

After the markets' best year in more than a decade, 2014 got off to a slow start on Wall Street. All three major stock indexes, as well as the Silicon Valley 150, declined about 1 percent.

2013 could have not have been much worse for Zynga, the San Francisco online gaming giant, but 2014 is starting better. Shares rose 15 cents, or 3.9 percent, to $3.95, on word that new CEO Don Mattrick is focusing on more engaging role-playing games, which could keep users playing longer. There is also optimism for big revenue gains from its overseas online-gambling efforts, which could add $6 billion in revenue over the next two years, according to reports.

Intel dropped 16 cents, or 0.64 percent, to $25.79, as CEO Brian Krzanich told Re/Code -- the newly rebranded All Things D site from Kara Swisher and Walter Mossberg -- that the Santa Clara tech giant is looking to offload its Internet TV plans after failing to reach content deals with studios and networks.

And after a two-day stumble last Friday and this Monday, Twitter rose for a second straight day as it continued its inexplicable surge that has seen its share price leap more than 60 percent over the past month. Twitter ended the day up $3.85, or 6 percent, at 67.50.

Up: Gilead, Facebook, Zynga, Twitter, Pandora

Down: Apple, Google (GOOG), Oracle (ORCL), Intel, Cicso, HP, eBay (EBAY), Yahoo (YHOO), Netflix (NFLX), LinkedIn, Tesla

The SV150 index of Silicon Valley's largest tech companies: Down 14.72, or 0.98 percent, to 1,492.17

The tech-heavy Nasdaq composite index: Down 33.52, or 0.80 percent, to 4,143.07

The blue chip Dow Jones industrial average: Down 135.41, or 0.82 percent, to 16,441.35

And the widely watched Standard & Poor's 500 index: Down 16.38, or 0.89 percent, to 1,831.98

Check in weekday afternoons for the 60-Second Business Break, a summary of news from Mercury News staff writers, The Associated Press, Bloomberg News and other wire services. Follow Mike Murphy at Twitter.com/mmmmurf.