I think both courses are very similar. In fact, of all of the Doak courses that I have played, I found SS Blue and Ballyneal to be the most similar.
The obvious similarity is the greens. Both are wild, undulating greens that are the real challenge of both courses.
However, they have several similar holes:
SS Blue 6 and Ballyneal 7 (both very drivable par 4s that are usually worth the risk)
SS Blue 13 and Ballyneal 12 (both very drivable par 4s that are very penal if you miss)
SS Blue 17 and Ballnyeal 16 (both have really challenging/entertaining 2nd shots over/through a hazard
SS Blue 5 and Ballyneal 3 - both very short par 3's
If I had to rate both, I would give the edge to Ballyneal (more use of the ground and a more intimate routing), but both are really good.