Both has great aggro for single target but war is a little higher for a short amount of time.
When we're doing Ex titan on solo heal,cure III is greatly increasing the aggro of our WHM.Our war hold it easier,even if there is many crit because of berzerk+unchained who is giving a MASSIV burst damage for 20 sec.It's more useful on solo heal Extreme Titan.
But well,Ex titan solo heal is not a "common" thing so it doesn't really matter

Both a great and complete each other REALLY well actually.
I wish it would be the case for MNK +DRG by example