Some people may love Sony a little too much, which may lead them to believe the console market is "like a romance", but that's basically ridiculous.
What makes a console a success? Conveying value. Like any other consumer product.
When I first began my armchair analysis back in the Dreamcast days I made a lot of errors in my analysis, mainly because I was out of step with what was truly considered "value" for the consumer. I didn't realize how valuable EA support was, for example, or the fact that Shenmue had very little value in the eyes of the average casual gamer.
All this vision stuff is nonsense. The average gamer doesn't care about any of that. What he cares about is value. Successfully conveying that value is what makes a console a success.
What does all of this mean? Well, the games/features are the "value" and the marketing/branding is the "conveying" of said value. You can absolutely consider all this vision talk to be part of marketing/branding and Sony has an advantage there, but its not the whole story. All the vision in the world isn't going to do you much good if there is no actual value in the end.
The reason I think MS will gain some ground against Sony is that I think they will create more value with Xenon in the form of better games and convey it with stronger marketing/branding than with Xbox.
The main thing I think we can argue about is what constitutes value for the consumer and who is going to convey that value most strongly.
Some things of value to the consumer might include:
HD-DVD/BR playback
Known franchises they want to play
Great new games they want to play
Their friends have the same console
Backward compatibility
Other features like hard drive storage, networking etc...
I think that of these last generation, DVD playback and game selection were the main reason why Dreamcast lacked value and PS2 had value in the eyes of the consumer. Add to that the fact that Sony was much better able to convey this value with marketing/branding, Sega didn't really have a chance. Later on, DVD playback was not really as much of an issue, as most new consumers already had a stand alone player.
People didn't buy PS2 for its "vision". That's ridiculous. They bought it to play DVD movies, GT3, GTA3, MGS2, FFX, and EA games. That's the reality. Sony vision may have been responsible for excellent conveyance of said value, but its not the whole story.
Going forward I expect games to be the big driving value next generation and expect Sony/MS to be pretty close in this regard (just my opinion), mainly because MS will have EA support right away, good western dev support, Halo franchise established, and a one-year headstart on game development. Sony will have better Japanese dev support and a few other key franchises on their side like MGS and GT. I don't think BluRay will be a huge factor for reasons I've stated before, but I could be wrong.
As far as conveying value through vision/branding/marketing, Sony has the advantage here, although MS will not be as far behind as some people here think IMO. That's why in the end I think that Sony will lose some ground to MS, but will still probably win the race next time. The difference is that MS won't lose money and will definitely be right there again for round three.
Sony controls 70% of the market right now and looks like they'll settle in around 67-68% by the end of the cycle. Next generation I expect them to fall into the 55-60% range, losing ground to MS. I think Nintendo will be essentially static, but they might suprise us.
I'm open-minded about all of this stuff now. It's stupid to have allegiances with corporations or to hate certain corporations. It clouds reason and judgment. My Sega fanboi and Sony hating days are over, but I welcome MS as competition to Sony and think they will be more competitive next time around. All IMO of course.