I am well familiar with Hornbeam but I am almost not familiar with an holly. Therefore it is difficult for me to compare. But Hornbeam is good wood. If the hornbeam tree is cut in dry and cold winter that at accurate drying (better kiln than air) it becomes almost white and very dense. In cues for Russian billiards we use hornbeam for shafts and in the basic design of cues on butterflies. The hornbeam has a little bit big porous in comparison with a maple therefore sometimes it is more spoiled with a dust from dark wood than a maple, but simultaneously more rigid and firmer than a maple.
I tested a hornbeam on shafts for pool cues. Results quite good. For the handle it is very good wood. Example of the white hornbeam handle here.
http://forums.azbilliards.com/showthread.php?t=122091
In Russia is a technology of painting of hornbeam in black color on full depth. Very not bad looks and has no "superfluous" weight as an ebony for example. Here cue with the handle from black hornbeam.
http://forums.azbilliards.com/showthread.php?t=115584&page=2