Titleist throughout the bag. At first it was brand recognition, then just for consistency and familiarity, even while being professionally fitted. Then during my last full bag fitting I entered the experience with a different mind. The major brands had all made such significant strides in equipment I felt if I married myself to one brand I would be selling myself short in my game potential. So I instructed the fitter to NOT tell me anything about the clubs he would put in my hand until he reached a tipping point of selection for each group of clubs. (woods, hybrids/long irons, irons, and wedges).
So at the end of it all I still ended with a full bag of Titleist clubs, with the exception of a Tour Edge hybrid 3 iron. So for me now I suspect you would say it is dedication to the best product for me.
PS: Caveat to this is that I actually did have one set of irons that performed better during the fitting, Epon forged blades, but they were outside my budgetary constraints.