Neither is particularly necessary, but neither are they particularly horrid. Usually, though, there's at least one blurb a week that makes me groan. They're unnecessary, and if they are necessary, it's because the cover artist didn't do a good enough job. The cover should grab the eye immediately, it should make the reader want to know what's inside, it shouldn't make the reader read a blurb and know what's inside. There is no cover so good it can't be ruined by a bad blurb.
Blurbs are a throwback.
We don't need them. Probably about the time they became annual, actually, and thus were something expected instead of special. In other words, they were never that great an idea in the first place, and they've certainly worn out their welcome now. They can serve as tryouts for new talent, but that's a rare thing these days, and while I'm all for new talent having an outlet, foisting unknowns onto the unsuspecting fans of a character for double the price they pay to get established talent seems a cruel trick. They can also serve as a spotlight book for big name talent that don't have the time or inclination to do more than one story, something to let them tell a big, self-contained story.