Blood+ is a story inspired by Blood the Last Vampire which was made before the series did. This is why many people tend to compare both anime.
I watched Blood+ before Blood the Last Vampire, and as a result Blood+ is better...but that's my opinion. It may vary from people to people of course.
The very first episode is already excellent enough to capture my heart and interest. The music itself fits the scenes very well and adds up to the actions and emotions in this anime series.
If you love romance and a slow but action-packed series, Blood+ is your answer. Although it may be violent to others, it's a must watch if you love vampires and sword-slinging girls.