Scintillating Sun Shards is generally regarded as the more effective of the two.
This is for several reasons- namely that fiends are typically regarded as being far worse than beasts, and that to make Deadly Splinter more effective than Scintillating Sun Shards, you'd have to just naturally have charge time reduction max and bomb damage max. Even then, whether or not you value the stun effect would come into play.
My opinion is that the Sun Shards and Deadly Splinter Bomb are novelty items to begin with, as Dark Briar Barrage is just that much better due to not having invincibility frames, dealing consistent damage without disappearing randomly, and allowing the user to take out grievers without mastering every detail of the game beforehand. But the new shard bombs are still cool items to go for, and they are a ton of fun to use even if they are a bit worse than every single alternative barring winmillion and the iron slug. That being the case, I would still recommend sun shards, because stunning enemies + dealing with fiends better makes it more interesting to use.
(I really should be asking Zeddy this but here we go)
I am still curious of shards bombs and have no idea which ones to craft. My problem is that i'm stuck between crafting the SSS (Scintillating Sun Shards ) and DSB (Deadly Splnter Bomb). The SSS has a damage bonus vs fiend: very high and a fair chance of moderate stun however the DSB lacks both of these bonus's in exchange for MOAR damage...........So I ask. Which is the better bomb?
Many Thanks