There is basicly not much of a diffrence between blue´s and blacks. The blacks come with a 5 year warrenty, and have a slightly beefier chasis then the blue´s mainaly. But thats mostly it, in terms of performance not much of a diffrence.
They make the Black drive in sizes up to 4TB. The Blue drives do not exceed 2TB. I haven't shut down my RAID0 machine since I got Linux installed 3 months ago. The Blues on my gaming rig have been running for a long time over several machines. I say flip a coin