I've done most of my stuff in Dacite on Obsidian. I think, depending on the grade, dacite is great. Some dacite knapps more easily than others. The stuff that is almost bassalt but still glassy is tough and really sharp. I like to make points from this that I would want to stand up to some punishment. But Obsidian on the other hand is still sharper and will kill a deer or any other animal just as well.
Just my two cents worth!