To access treelab just create a tree and click on the little "E" in the box. (I don't know if the demo has it). IMO Bryce and Vue are both awesome programs some give and take of course. Generally speaking, I like Vue's preset plants a little bit more than Bryce (especially the coconut palms), of course I wish it had the control of plants that Bryce has. IMO Bryce is great for modelling buildings/robots/architecture, maybe better than Vue. Vue's skys look like they have more volume than Bryce's. Both are capable of almost the same things, slight differences.