It actually completely depends on the kind of tree, and the explosive power. But look: Shrapnel is very little mass of the bomb. It hits at random. If it hits, it hurts, but you have little chance of being hit overall.
Splinters from an exploding tree are actually like a wall of needles.
Which cant pierce heavy cloak and loose their killing power within meters, while metal fragments retain killing power for up to a hundred meter range.
Hence metal fragments (especially light ones) have much more killing power and deliver most casualties on the modern battlefield (thus extensions on the american bulletproof vests and current russian BZK are necessarily).
So I think that in most cases wooden splinters would cause by far less casualties than even the HE blast from the same projectile and trees would shield troops from metal fragments (except heavy ones, which can penetrate 20mm RHA) and disrupt propagation of HE effects in the area.
We need more missilez code for the missilez god.
"Tactical Ikalugin inbound on this position in 10... 9..."