For .veg plants all of the makers who have been mentioned here are good. I have plants from all of them and have been very happy.
For static plants I have used mostly those form Lisa's Botanicals (via Daz) and RDNA sources.
I will often use plants from 4 or 5 or more makers in a single scene.
I've tried making my own and it's hard work, so I have a great respect for all of those who have specialized in this area.