Responsive web design — a method of designing and developing websites such that they display well on a range of devices — is a seductive concept, especially for banks that struggle to maintain mobile banking apps for iOS, Android, BlackBerry and Windows devices. The ideal is the company has one set of code, one product to manage and it's set, no matter what smartphones and tablets customers are using.

The reality is not so simple, and a debate is going on in the industry around how useful responsive design is, and whether or not it can replace native apps.

"It's very popular," notes Clay Almy, executive director, integration and JEE Services, financial services at Blackstone Technology Group, an IT consulting firm based in San Francisco. "I think it's a shiny bauble. Often an architect inside a bank will have bumped into it, thought it was cool, and maybe not considered the fact that it was more relevant to his content website of choice, such as the Washington Post, than a transactional app for a mobile device."

The real battle, he says, comes down to what customers want to use. Banks will then have to decide whether they are going to predominantly focus on maintaining a mobile web-based solution or continue down the native app route that many have taken, which is inherently fragmented and costly.

"In a lot of cases, banks don't yet have a grasp of what their customers want to use and what's the easiest way for them to handle this," Almy says. "There are times where mobile web is fine, there are other instances where you want that sleeker, richer app experience. I see value in responsive design, but I don't necessarily see it being brought forth in a way that's aligned with what customers are clamoring for. It's early days."

Almy's colleague Ken Hans, executive director, financial services at Blackstone, has an even stronger take. "I think it's a silver bullet concept in theory. In practical implementation, it isn't that straightforward. It's won the hearts and minds of some vice presidents of business, who think they're going to create one style sheet that will roll down to any device."

U.S. Bank in Minneapolis, which has led much mobile banking innovation and knows that half its mobile banking customers use its mobile browser, uses both responsive design and native apps.

"What's important is that we listen to our customers and act on what they tell us," says Niti Badarinath, senior vice president and head of mobile banking at U.S. Bank, who spoke to BTN in a recent interview. "Not only are we going to continue to build things that are responsive/adaptive, know what device you're coming from and optimize the experience, we have a user experience team that is constantly improving the experience. User experience is one of the key sources of differentiation for us, and it pervades everything we do — what features we build, how we build them, how we expose them."

Some banks, including Citi, are adopting a hybrid approach, using HTML5 (the latest generation of hypertext markup language used to design web pages, one that supports graphics) and app "wrappers," also written in HTML5, that help the code look and feel like a native app. Citi's developers have used HTML5 to create a global tablet "app" and a wrapper that can be downloaded from Apple's App Store. The bank can refresh the pages remotely. The look and feel is identical to Citi's existing iPad app. So far, the app-like site has been rolled out to customers in Russia and Hong Kong.

In the end, hybrid approaches like this may be the way for banks to maintain one code base, yet offer a rich experience across devices.