I create YouTube tutorials for e-on on PlantFactory and have worked for them on a freelancer basis for many years, after having used both softwares for more than 15 years. An update for R21 for Vue is not out yet, but the current version works fine in R20 and R21 is supposed to be supported soon. Is there anything in particular you would like to know?
I am probably a little biased as I do freelancing stuff for e-on and I am not allowed to say too much of what's going on behind the scenes, but e-on has put a lot of effort in the last two years to gradually catch up with the industry standard. While a full core rewrite like with C4D is not currently underway, dozens of issues have been fixed (and are still being fixed continuously), code and modules are refactored one by one and the software opens up very much towards professional pipelines. Subscription model and pricing aside (as this is more of a sales topic and less a development topic), the current subscription version has introduced support for OpenVDB import and export (including animation) for bringing Vue's cloud layers into other DCC apps, LOD baking and exporting (billboards included), support for PBR and Substances, gradually more features for the Path Tracer (unfortunately at an even slower pace than ProRender updates in C4D, but still...), more texture baking options and - released just two weeks ago - a first tech preview for native import of PlantFactory species in 3DS Max and Maya, with C4D, Blender, Houdini, Unreal etc. supposedly to come next year. Also, for PlantFactory, more realtime integration options are planned. Integration plugins are also very stable now and are supposed to be gradually revamped over time as well.
Cerbera has lots fair points on e-on's past problems and mistakes, but a lot of these things have changed by now as well. Tech support is really good nowadays and while the subscription model has the same Pros and Cons that we have to tackle now with MAXON's move away from MSAs, it helped at least to consolidate the product palette into two versions, differentiated only by export options and rendering resolution (the software features themselves are identical between Creator and Professional versions), and to release a new update every quarter with more focus on stability and pipeline integration.
I don't want to make a sales pitch here, but I wanted to give a bit of insight from someone familiar with the company and tools that things are indeed changing drastically at e-on, even though at a slow pace. Subscription or not: due to the ongoing fixes and code refactoring, the current versions are the best yet, with lots of work still to go for the developers...
And as for PlantFactory, the software has always been really stable from the very beginning and is overall more powerful than Speedtree. The learning curve is steeper, though.