Once you see Segment PRO, you'll start to see how radically different these programs are. They both build segmented vessels, but there is almost no similarity. It kinda comes down to this - if you need to build a bowl that can only be designed in Woodturner PRO (staves, compound segments, unusual design objectives), you need to build it completely in 3DP/Woodturner PRO. Once it is done, it cannot be opened in Segment PRO because it has staves or compound segments. If it isn't unusual, it will take you longer to export it than design it from scratch in Segment PRO.
The target for Segment PRO is those turners that want to design a bowl rapidly and would rather spend time building the bowl instead of designing the bowl. If there is a need to add rows one-at-a-time so that you can have each row or every other row be different then Woodturner PRO is for you. But in the time it takes you to do that, you could have designed 20 bowls and selected the one you liked the best in Segment PRO.
Lloyd