Amit Singh spent 20 years at Oracle. Then he left for the clouds.

MOUNTAIN VIEW, Calif. — Amit Singh defected to Google after 20 years at Oracle because he wanted to join the revolution in the cloud. In May, he took over Google’s enterprise operations, overseeing the company’s effort to replace traditional business software with new-age web services such as Google Apps and Google App Engine. Since his move, Oracle has uncloaked its own “cloud” services. But for Singh, that’s a little different.

“I don’t know what there is about Oracle’s cloud that is really the cloud,” he told Wired.com this week. “[Oracle CEO] Larry [Ellison] has never been a big supporter of the cloud. He’s recently made some changes, but Oracle are very much a traditional on-premise company.” An on-premise company is an outfit that sells hardware and software to businesses for use in their own data centers. Google is in no way an on-premise company.

This week, over 350 businesses sent their chief information officers to Google headquarters in Mountain View for a mini-conference where the company spent two days pitching its ever-growing collection of enterprise services, and Singh was among those putting on the hard sell. He runs worldwide sales for Google’s enterprise business as well as operations.

On Monday morning, Singh told all those CIOs that Google is now offering round-the-clock phone support for all issues involving the core services in its Google Apps suite, and then David Girouard — the man who essentially founded Google’s enterprise operation — unveiled some new tools for managing smartphones that use Google Apps. But these additions served Google’s larger message: that its web-based services are more flexible and reliable than traditional “on-premise” software — or even the cloud services now offered by the likes of Microsoft and Oracle.

The basic pitch is that with Google’s services, your data and your applications are always with you — whether you’re on a desktop PC or a laptop or a smartphone — and that Google’s back-end infrastructure is more advanced than what you see from companies who’ve only recently entered the web game. Google uses what’s commonly called a “multi-tenant” setup, distributing the workloads for all customers across an infrastructure that spans multiple data centers. This reduces not only downtime, the company says, but costs. Google Apps includes a service level agreement (SLA) that promises its services will be available 99.9 percent of the time, and businesses can use the suite for a subscription fee of $50 per user per year.

According to Google, all this has led over 4 million businesses to adopt Google Apps, with 5,000 jumping aboard each day, and during his Monday morning speech, Singh made a point of saying that “thousands” of these daily converts summarily switch off servers running Microsoft software.

Microsoft is offering its own web-based suite: Office 365. But during a lunch briefing with reporters — and later in conversation with Wired.com — Singh said that when Google speaks to potential customers about Google Apps, Office 365 almost never enters the conversation. “Microsoft is competing mostly using its on-premise stuff,” he told us. “By and large, customers either want on-premise or cloud. And if it’s cloud, it’s Google.”

His comments were largely a response to recent PR from Microsoft. On the eve of Google’s conference, Microsoft unloaded more than one blog post that pumped up Office 365 at the expense of Google Apps. The two companies have long enjoyed a spirited back-and-forth over their enterprise products, and when told of Singh’s comments, Microsoft’s senior director of online services was only too happy to respond.

“With Google, all they have is cloud,” Tom Rizzo told Wired. “Of course they’re going to say that when someone goes to the cloud, they’re going to go Google. It’s bit like whenever you have hammer, everything looks like a nail.” His point is that Office 365 is meant to compliment Microsoft’s local software — and that its dual-offering is exactly what many companies are looking for.

This is only what you’d expect from a company that spent the last thirty years building an empire on local software. But Rizzo points to studies from research outfit Gartner that indicate only 3 to 4 percent of businesses have moved even their email to online services like Google Apps — and that this figure won’t reach 20 percent before 2016. “Email is the first workload to go. So users aren’t moving wholesale to the cloud,” Rizzo said. “We see customers wanting to move part of their operations to the cloud, but keep some of it on-premise due to regulatory requirements and security requirements.”

He also points out that local software lets you work when you don’t have an internet connection. Google has only recently revived versions of its primary services that work offline, and these still carry a “beta” tag. Comparing Google’s offline tools to Microsoft’s desktop software, Rizzo said, is a non-starter. “It’s like comparing a Pinto to a Ferrari,” he told us.

Naturally, Google argues that Microsoft’s past is more of a hindrance than a help. Desktop software is needlessly cumbersome, the company says, and though Microsoft has moved to web, it hasn’t yet dropped all that extra weight. “365 is their first attempt to try to do what we do: a pure cloud, SaaS [software as a service], shared environment,” Singh said. “They’ve taken the core of Office 2010, and they’re trying to create this multi-tenant architecture. It’s very hard to retrofit that into a software layer. We tried to do that at Oracle.”

With its new cloud services, Oracle is offering its various software tools over the web, including its database. But it hasn’t adopted a Google-like multi-tenant architecture. Ellison says that in keeping customers isolated from each other, Oracle provides better security — whereas Singh sees this as an inability to really cut costs.

There’s no settling these arguments. There are certainly advantages to Google’s model — we’ve seen them firsthand — but no doubt, there will be businesses who refuse that model for years to come. But Singh’s point is well taken. At Google, “the cloud” means something very different than it means at Oracle. Or Microsoft.