Spent a good part of the day reading up on the PE issue and it seems clear that LL doesn't want big builds using mesh. I guess that makes sense. It's not hard to imagine what might happen if people could upload huge mesh items (without the constraints PE enforces).
That said, it doesn't make much sense to see a 20m mesh build using 2/3 the faces of like sculpts and have the mesh produce an 85 PE tree when the sculpt tree uses 5 prims at any scale. Even the least efficient 1 sculpt per tree limb, branch, trunk approach produces a tree with less than 25 prims and at any scale. Seems a bit crazy and way outdated to make meshes so much less efficient, ie high PE ratios. Personally, seems like a fixed, non-scaleable mesh/size alternative makes sense.
The other issue I've seen argued regarding PE is in selling larger mesh items. How do you sell a scaleable 10m, 20 PE tree to someone who then scales the tree to 25m only to find they've used 80 prims on their prim limited land without getting questions, complaints, etc? That issue alone, absent grid wide user education, seems to relegate meshes to niche for large item builders.
It is what it is. I'm back to sculpteds having wasted a week working out the (in)efficiencies of meshes.