FORTUNE — San Francisco’s Moscone Center is no stranger to developer conferences. It’s been home to the annual geekfests hosted by Apple (AAPL) and Google (GOOG) for several years. But this summer, Microsoft (MSFT) decided to join the fun, bringing its three-day event to San Francisco. (Last year’s conference was at–you guessed it–the company’s Redmond campus.) All three companies are vying for developers’ love–they run competing platforms, like Apple’s iOS, Google’s Android and Microsoft’s Windows Phone on the mobile front. But their approach to developer conferences is also different (one similarity: parties are a must). As Microsoft winds down with its extravaganza, here’s a side-by-side look at the Bay Area’s dueling developer events.
Microsoft BUILD
When: June 26-28
Attendees: 5,000
Highlights: Windows 8.1, an improved update of its PC operating system, was announced. Also, a Facebook app is finally coming to Windows.
Oprah moment: Free Acer Iconia W3 tablet and Microsoft Surface Pro
Party: DJ Boogie was in the house at Wednesday’s night’s VIP event (he used a song-mixing Windows 8 app called edjing for his performance).
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Google I/O
When: May 15-17
Attendees: 6,000
Highlights: Google Play All Music Access, Google’s (long-winded) foray into music streaming and updates to Chrome and Google search. Also, a Larry Page sighting–the elusive CEO took questions from the audience.
Oprah moment: Chromebook Pixels for everyone
Party: let’s just say Billy Idol was there
Apple Worldwide Developer Conference
When: June 10-14
Attendees: 5,000
Key announcement: the latest version of Apple’s mobile operating system, iOS 7, featuring a “radical” redesign. Also, Apple marketing exec Phil Schiller used the word “ass” (as in, “Can’t innovate, my ass!”).
Oprah moment: None
Party: Developers rocked out to Vampire Weekend, iPhones in hand.
