1. DL is not poor and strange, it's a direct light algorithm so it works like Blender internal if you want. Very useful and fast for opened scene like exterior or product/studio rendering. The Audi ( http://www.yafaray.org/gallery?g2_itemId=4738
) was rendered with DL and as you can see, it's quite efficient.
2. Photon Mapping is my favorite. Really good speed/quality ratio, specially for interior rendering. Yafa get one of the best Photon Mapping method I ever used, so accurate that you can use it for exterior scenes.
You just need to know how to use it and ( i promise) you will like it
3. SPPM is quite strange for me, sometimes it provide good results, sometimes no. I have to practice more to get good results, but I can say it AA passes are very fast in this method.
4. PathTracing is an old method but unbiased and the more precise and physically correct. The best for exterior ! But yes it's still slower, the new Russian roulette can help on this.
5. Bidirectional PathTracing is good engouh for some rendering, I like the fast AA passes and the " progressive" rendering of it. Maybe this method could be used for 3D preview and GPU acceleration like Cycles...
I believe that Yafaray need to stay in an "easy to use" stage, material system should look like the one inside Corona Render.
For Color management, you can use too the Tonemap node in post-compositing, it provide very good results without Filmic !
I'm working on a Render Engine Comparison including Yafaray and the downloadable scene will be a benchmark too ( interior rendering)... stay tuned !