The specs on the blu-ray discs themselves, especially in terms of protective layer thickness concern me. HD-DVD dics have much thicker protective layers. Additionally, blue lasers are more expensive and the density provided by a blu-ray disc doesn't escape what is possible using plain, cheap, and proven red laser technology.
If the density were significant compared to that of what is possible with red lasers and they showed more concern toward durability in general, I'd cast my vote for blu-ray. Currently, I'm for HD-DVD.