Keynote has ranked Chase's mobile banking app the top in its class for the fourth time in a row. The bank's leadership is based on the fact that it offers robust functionality, a strong user experience, and streamlined navigation, according to Susan Foulds, manager of the Keynote Mobile Banking Scorecard.

That said, scoring among the top-tier banks - Chase, Bank of America, Wells Fargo and newcomer U.S. Bank -- is tightening, Foulds says.

"We're seeing improvements across the board among all the banks," Foulds says. "They're filling in functionality, improving the user interface and navigation. We're seeing more capabilities to shop and select deposit accounts and credit card accounts on the mobile device. In a few cases, banks are letting customers open accounts on their phone."

Banks are streamlining the number of clicks or swipes a customer has to go through to complete a task. They're providing easy to use tools, such as a full calendar to select dates in setting up payments and funds transfers.

Keynote, which is an application testing and monitoring software provider, examined the mobile offerings of fourteen large banks and USAA in four modes -- text, mobile web, iPhone app and Android app. The institutions were Bank of America, BB&T, Capital One, Chase, Citibank, Citizens, Fifth Third Bank, KeyBank, PNC, Regions Bank, SunTrust, TD Bank, USAA, U.S. Bank and Wells Fargo.

In the fall 2013 scorecard, the company found that Chase performed best in two of the four categories -- ease of use and quality and availability, while Bank of America took first in functionality and Wells Fargo led in the privacy and security category.

In the past year, Chase improved its user interface, especially for payments, Foulds says. "They have the most options for types of payments," she notes.

The bank extended access to account information on mobile devices. It increased the amount of transaction history it lets customers look up. It also let them see their reward point balance, view prepaid card balances, and load value onto their prepaid cards.

U.S. Bank moved up this year in the scorecard to tie for third place. "U.S. Bank filled in some functionality," Foulds says. "They also came up with mobile photo bill pay capability."

All the banks are trying to fill in capabilities that are important for mobile users, but at the same time improve customer experience and navigation, Foulds says.

One common theme is a persistent and centralized menu, so that within one click customers can get to global navigation.

Another trend is banks are offering more self-service tasks, letting customers do more without requiring a desktop computer. They're letting customers add bill payees and person-to-person recipients from their smartphone or tablet, and in a few cases they're letting customers register for mobile banking via mobile device.