Have to say, that we don't have a lot problems with Xfrog Plants
/ HQ Plants
models reported and if some issue appears usually it's fixed very quickly. Actually there are about 3000 Xfrog models in total, so feel free to ask directly on Xfrog's forum
about package(s) you are interested in. Generally, hard to say which models suits best to your scenes. As posted here
"Each library has its own pros and cons. HQ Plants include native materials for VRay and Mental Ray and doesn't use opacity maps (renders may be slightly faster). XFrog catalog is much more larger and includes species that are not available in other libraries.
In any case, both includes free samples, so users may evaluate them and see what fits better to their needs."
The same in case of Laubwerk
models. As there are free samples available, probably the best way is to do some tests with them and than decide.