Well one of the things about the HD that will begin to be there now that wasnt there as much for xbox is...
the ability to get updates and patches for games. i know many console gamers will say that its just the developers rushing the game and they should take more time to make sure everything is good. but thats just not the case, online games NEED patching, with all the players that go thro and play it and find bugs, exploits and cheats, there NEEDS to be a way to fix thoes problems. No amount of developer time can take care of every problem that will come up in online games.
Xbox gamers started to see just that in Halo2's online, exploits will be found and used.
The more and more games go online, the more they're going to start needing a HD to give the full power of what online games can provide.
Though, for many things, sure developers can make it so people with a HD can use and ones without dont need. more work for the developers tho and might just leave it out all together to save time. However the things like updates on online games can only be done if everyone has the space to save the patches. thats where a HD not stardard hurts a lot.
However this isnt exactly hurting 360 this gen unless PS3 throws a curve ball and sony desides on a HD standard.
And i wouldnt be so optimistic on the price issue just yet. im betting the prices will be even, especially after reading that the latest speculation, which might be from sony itself is that PS3 will be below $400, possible at PS2's launch price point wich was $300. (just for the record, i dont think it will be as low as 300 unless sony releases a core package too) however i guarentee it wont be over $400
and yes dont worry, im trying to find where i read that last be right now.
[edit: Actually its quite easy to find, theres a lot of sites reporting the same thing right now... Engadget has and interesting idea on it, heh and interesting enough at the time they wrote that, it was a couple months before this latest price speculation]
http://www.engadget.com/entry/1234000443056098/
http://www.1up.com/do/newsStory?cId=3145024
Right now tho, i'd like a 360, however im not spending the money on a console at launch anymore. first years always suck and its just not worth it. i'll reconsider after the first price drop. (goes same for PS3... as for nintendo, maybe in thier 4th year when it gets to $100 and they release the first zelda for it... other then that im tired of the dust collecting machines)