They are "slower" in that actions take longer, mostly because so much data has to be serialized, encoded, shipped long distances, decoded and deserialized before rendering, but they're "faster" in that updates happen instantly and transparently.
Desktop software used to be very quick to respond locally, but updates would take weeks, months, or even years to get pushed out. Some applications, once sold, would never, ever get an update. You'd just buy the new version whenever that came out.
Flip side of that last one, sometimes you would even buy a program, and it would still work long after the company that wrote it went out of business. These days, when a company pulls the plug on a web app, you are SOL.
When you buy a license for a desktop application, the price you pay includes tech support and often times future upgrades. When the developer goes out of business, you lose out on all of that. In contrast, the vast majority of web apps are on a subscription model - as long as you continue to pay, you're getting your money's full worth. Sure, it can be a bit disruptive when the company pulls the plug, but in most cases there are reasonable alternatives that are both easy to discover and easy to start using (usually within the span of minutes).
Which is, btw, another incentive for web companies as it forces large companies who do decide to make use of a web product integral to their operation willing to pay a lot more to keep the web company alive.
I'd take a software-as-a-service solution that I can replicate the data from in an open standard format like JSON or XML over a closed-source application with an impenetrable binary file format any day.
That seems like a false dichotomy. There are SaaS applications with no data export option, and there are closed-source locally installed applications that use textual data formats (e.g. XML), if only as a matter of convenience for their developers.
I mean this by way of comparison to applications that were distributed on floppy such as WordPerfect, dBase, FoxPro and so on, where the data format was proprietary.
It's only relatively recently that we've seen open-source and open-data applications. These are arguably better but relatively rare.
I think you're right, and I like web applications and think they are a good avenue. However, looking at mobile apps and how updates work there, it is a nice middle ground. No doubt it's more essential as we're talking about phones, not desktops. But I think this sort of computing has come back in some ways.
Desktop software used to be very quick to respond locally, but updates would take weeks, months, or even years to get pushed out. Some applications, once sold, would never, ever get an update. You'd just buy the new version whenever that came out.