There’s a lot of discussion going on about whether – and why – consumers will choose to buy tablets (mostly running Android) other than the iPad, and, to a lesser extent, smartphones (mostly running Android) other than the iPhone. As usual, pundits and analysts predict that Apple’s dominance must inevitably erode, while John Gruber (@daringfireball) and a few others argue that they’re wrong. Gruber calls the debate “perhaps, the most polarizing topic of punditry in tech today.”

The pundits’ argument is based on sensible Econ and Strategy 101: Apple is making a killing now, but that’s because it was first out of the gate with these products, and without some kind of protective moat, all good things must pass, right? Apple doesn’t seem to have an insurmountable barrier or killer app (like iTunes with the iPod). Therefore, the fast followers will catch up on Apple’s hardware capabilities and apps, and price-compete their way to share. The only question is how long it will take.

One big counterargument, of course, is that Apple has core competencies that not only got it out of the gates first, but enable it to run faster too – particularly in innovation and design. By the time Samsung caught up to the iPad, the iPad 2 was already around the next corner.

In the tablet market, Gruber, John Paczkowski and others make a second argument too – that catching up to Apple isn’t good enough. To really win, a competitor like Samsung, RIM, or Dell has to provide a good answer to the question “why should somebody buy this instead of an iPad?” But this only hints at the much bigger moat Apple’s built around itself: its brand.

Many techies see a brand as an elaborate marketing ploy companies use to appeal to the emotional part of consumers’ minds, and a lagging indicator of success. In other words, you can fool consumers for a while, but your brand will stay strong only if the products are; either way, a brand doesn’t itself create lasting success.

This misapprehends what a brand really is: a promise in the mind of consumers. Unlike, say, five years ago, today most of the extremely high value of Apple’s brand doesn’t come from its ads, its fanboys, or even its retail stores. It comes from average consumers’ experiences.

Imagine a non-techie thinking about buying a new smartphone or a portable computer. Even if she’s never been in an Apple store, there’s a decent chance she got an iPod Nano as a present at one point. More importantly, she almost certainly knows many people who have bought an iMac, iPod, iPhone, MacBook, or iPad over the past decade, in various versions and combinations.

What impression of Apple has this given her? Almost certainly, it’s been overwhelmingly positive, because Apple hasn’t launched a crummy new product in a long time – and that includes both new-category (iPad 1) and next-gen (iPhone 3GS) devices. And here’s the key – when it comes to sales, it’s OK to have a bunch of misses, so long as you have a few big hits. But with a brand, misses hurt. People hate wasting money, and they know they’re taking a risk when they buy a major new piece of technology, same as when they go to a pricey new restaurant. If people talk about how a product kind of sucks, that won’t just hurt sales of that product – it hurts sales of the next one too. The opposite is also true.

Four or five years ago, even if you heard great things about Apple products, it was still acceptable to brush them off – sure, the iPod was cool, but I’m not sure about this new phone. But now, in consumers’ minds, Apple has been batting pretty close to a thousand for a decade. And that’s its best asset – the fact that you can’t sneeze without hitting five people who’ll tell you they love their iPad, will never switch from their iPhone, or that their Macbook “just works” – and zero who say otherwise. In other words, it’s the brand. We’ve been surrounded by great Apple experiences for so long now, we’ve been trained what to expect – if Apple announced it was coming out with a washer/dryer, we’d laugh, but we’d also immediately form some positive expectations about how it would look and function.

That’s why it’s getting harder to defend buying anything but an Apple product: simply because you can be confident you’ll like it. Tech mavens might always be willing to adopt the “best” product, but most consumers are more wary. If Samsung, RIM, Dell, or anyone else today announced a tablet that had 13 good reasons why everyone should buy it instead of an iPad, tomorrow most people would still buy iPads, because the one reason that really matters to the average Joe is risk. Technology is complicated and often disappointing, but Apple’s brand credibly promises people that they’ll love the next thing they buy that has a little bitten apple on it. Other tech brands can’t do that without sounding like the Boy Who Cried Wolf. And one great product won’t close the credibility gap – they’ll need a decade of great products, with almost no misses. The kind of trust Apple’s built up creates incredible momentum. That’s why the “tablet market” is Apple’s to lose.