it depends on your style preference. d+M has a different style of flourishing than DnD.
However, I would go with Dangerous if your going for just flourishes as it has twice as many flourishes in the DVD.
What is your skill level? I would say that the flourishes from the Trilogy are more difficult and better overall, but that's just me. Even though Dangerous is great and has a ton of flourishes, a lot of them are just minor variations that you could've worked out on your own.
Yeah... As the guys above me have said - it does depend a lot on skill level but also style. d+M and D&D have different styles. You won't go wrong either way if you practice though.