Melty Blood manga is definitely not as serious as Tsukihime proper.
But I just recently reread the Tsukihime manga, and I can tell you that it is fairly faithful to the first arc of the VN. It brought back a lot of memories for me from my play time. More so than the anime for sure. The anime was pretty generic.
Keep in mind that it isn't even as long as the 1st arc of Tsukihime really (since when you play the game you get a lot more conversaion and dead end play), and there are FIVE arcs to play through in the VN. They're all AWESOME though (except Ciel's... I honestly skipped hers I dislike her so much), and WELL WORTH playing through.
So Manga >> Anime. But VN >> Manga (yes, even more).