I guess it depends what you want to use them for.
I own both soft and stretchy as well as the typical FA non-stretch zip off pants. I hike mostly in the Drakensberg, and if I stay on paths then either will work fine. There are, however, areas like the approach to Ships Prow pass where one hike will absolutely destroy them.
The soft version works better if you have to do a lot of stretch work, i.e. climb over high boulders etc.
I do find the stretchy pants tend to run hot, perfect for winter, not so great for summer hiking.
Lastly, zip-off pants. I own a bunch of them and have only once used this feature. Granted, it was on a super hot day. Never used it since, but, different people have varying heat tolerances.
If in doubt, buy all 3 and test them out