The strength of Luxcore is its unique light balance, which is even better in Bidir than in Path.
PhotonGI is biased and what kind of light mood it will produce remains to be seen once it's finished.
I wonder what the cache sizes will be on complex scenes and if it all fits into GPU ram or what happens to render speed if it doesn't.
Also it is possible to use a photon cache for indirect light importance sampling in Bidir and Path (slower than direct lookup but unbiased with no splotches ).
There are lots of very interesting combinations possible...