I vote for Blu-ray because of it's capacity.
Most articles about these formats fail to mention computer users who archive a large numbers of files.
Currently on a SL DVD, I can store 1260 files from my karaoke collection.
A Blu-ray, (at 50GB), could store 14,600 of these files.
Instead of having to use 14 DVD's, I could only use one.

Back in the old days, I had my collection on CDRs and one DVD holds about 7 CDRs

Jon