The difference now are several factors...
There was but one format at the time of DVD. There are two formats now.
There was one other factor that I cannot remember...
Anyhow, I think it is irresponsible for Sony to create machines that lasts for 10 years. That's just stupid. In 5 years more, they'll come out with a new, better machine and all the good games will come for that machine, rendering the old one somewhat disappointing.
And the ten year cycle bumps up the price as we've seen.
Now, since it's due to last for 10 years, it does make sense to use a new optical media system, and there is nothing else for Sony to choose but Blu-ray. But from customers viewpoint, it's stupid. Today's games can fit on DVDs. But tomorrow's games - who can say?
So, had Sony made it a 5-year cycle, they wouldn't have had to use Blu-ray and everyone would win. Make it an add-on.
Blu-ray outsells HD-DVD right now and I can think of one reason. When you buy PS3, they stick the Blu-ray down your throat. So when you have to purchase it, why not use it for your High-Def means? Whereas on 360, people don't buy the add-on because they don't have to. They're waiting for the right time, as I'm sure many Blu-ray lovers would. But so again, why should they if they were already forced upon one?