By far, and the main difference compare with other
softwares, is the capability to create your own
Activities ID. This feature is a "must", when you do
Rhythmic programming, specially if you want to add or
modify activities later.
See prim75771 in the Knowledge Base for the
differences in P5 from P3. For P6 there are several
versions (6.0, 6.1, 6.2) each of which resolves
certain bugs and improves the WebApp. Prim74146 lists
what is new in v6.2.