onyx bolts do seem to hit higher, and make the specials occour more often. not many people use them tho, becouse they arent experienced with them...
i must admit dragon bolts(e) own's to, but they dont hit that well(except accocionaly high ones).
I would definitely have to say dragon (e) They are my favorite bolt to use and hit very high with spec but onyx hit higher and more accurate if you dont count the spec on d bolts.