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It's worth noting that HP was one of the first companies to back Blu-ray exclusively (see press release here and here). They withdrew their Blu-ray exclusivity mainly because the Blu-ray group refused to add in support for iHD (interactive content, based on XML - Blu-ray uses Java based BD-J), although they also demanaged Mandatory Managed Copy for Blu-ray which HD DVD already had, and the Blu-ray group accepted this change.
Microsoft is a big backer of iHD, and it is one of the features that separates Blu-ray and HD DVD, so you can see why the Blu-ray group were wary of adding support for it. There's really not much difference between iHD and BD-J anyway. It's funny that iHD (or HDi as it is known now) was developed by Disney, which exclusively backs Blu-ray which refuses to use iHD.
All these differences aside, the HD war really boils down to whether you support the studio friendly Sony camp, with it's DRMs and even more DRMs on top of DRMs, or do you prefer to the more "consumer friendly" (slightly less full of DRM, cheaper) Toshiba/Microsoft camp. In terms of actual consumer friendliness, neither formats pass the grade, it's more of an idealogical difference.