Sorry to say after working with Vue6 Infinite, Bryce Pro would have to be pretty damn impressive (ie exceed Vue 6) and beat the price for me to even consider it. For me all that Vue 6  is missing is particles and physics.

Vue 6 has a very easy interface, not as simplistic as Bryce but still very easy. The plant editor and ecosystem can't be beat. Animation wizard is a breeze. And realistic skies and lighting to die for.