Also, I think the regular plasma shots actually do more damage than the exploding orb (though not by a huge chunk). Testing it on large enemies seems to show that the exploding shot does very minor damage where-as the regular one does more and is more spammable.
That was my impression when using it first against a chimera, but then I did the same against a stoneclaw (one normal shot, take pic, reload, explosive, take pic, compare), and they were the same on a direct hit. Also, being more spammable doesn't do much when the hitboxes for ranged in this game are so tarded that half your normal shots will go right through the target.
Initially I thought I was seeing "more damage" because I was forced to make direct hits as well, but even up close I noticed some differences. I guess a controlled trial is ideal, I'll murder some town folks later :D
I just did a test on a mutated spider. Needed 25 shots of both kinds (all direct hits) to kill it.