On non-tablet PCs, Windows 8 can run on a 1,280-by-800-pixel screen, so you might argue that therefore Windows 8 will be just as usable on a small tablet as the same-resolution Android is. But that would neglect the fact that Windows Desktop apps are very dense, with tiny text and tiny buttons designed for a mouse's fine sensitivity and a large-screen monitor -- Microsoft has said its expectation is that people use a monitor with at least 1,920 by 1,080 pixels, and that's what the apps are designed for.
When you shrink those apps, you get a hard-to-use experience on the 10-inch screen of a full-size tablet such as the poorly received Surface Pro. You'll get an impossible-to-use experience on a 7-inch or 8-inch Surface Mini.
The other option Microsoft has is to deliver a small tablet that runs only Windows RT, the Metro-only version of Windows 8: a Surface RT Mini. The Metro app UI can scale to the smaller screen -- though not the special version of Office 2013 that ships with Windows RT. But there are few useful apps for Windows RT, and WinRT doesn't work with Microsoft's standard management tools nor does it support the common POP email protocol in its Mail app. In other words, Windows RT is a poor tablet OS at any screen size, and people simply aren't buying it.
Perhaps Microsoft could take a page from Amazon and ship a small tablet that runs Windows RT and rejiggers the Start screen to focus on its media services -- essentially a Microsoft Surface Kindle. But if you want media content, Microsoft's video and music library isn't as good as what Amazon and Apple offer, nor does it approach Google's library. Those other media tablets would make more sense, especially the iPad Mini and small Android tablets that give you more than media.
If Microsoft were to scale Windows Phone -- its other other OS that sports the Metro interface -- to a small tablet, users would experience apps that are blown up in size, creating an awkward fit. iPad owners have the option to run iPhone apps at double size, but anyone who has will tell you that you do so only in a pinch. No wonder most iOS developers create apps that autoscale to the device in use. But Windows Phone developers don't have this ability, so any Windows Phone-based tablet would be stuck with poorly scaled apps.
There's nothing wrong with the notion of a small Windows tablet. The problem is that the Windows Desktop was not reworked in Windows 8 to scale down; in fact, it essentially requires the use of large screens. And Metro by itself (that is, Windows RT) is too weak an OS to bother with.
Microsoft has boxed itself into a couple corners here, and it will take a radical move to break out. A smaller screen isn't that move.
This article, "Copying the iPad Mini won't help Microsoft," was originally published at InfoWorld.com. Read more of Galen Gruman's Mobile Edge blog and follow the latest developments in mobile technology at InfoWorld.com. Follow Galen's mobile musings on Twitter at MobileGalen. For the latest business technology news, follow InfoWorld.com on Twitter.