I have no experience with Taiyo Yuden. Maybe they have quality problems and you were unlucky enough to use them. Known, reputable brands which come to my mind are AVX, Vishay, Kemet, TDK.
Normally, dielectric defines things like capacitance stability over temperature, decrease of capacitance due to DC bias, these sort of things. Not directly reliability. Reliability is more a function of manufacturing process quality, capacitor size (density) and, of course, usage.
Soft termination capacitors are a valuable improvement for applications, requiring high reliability under harsh conditions (especially flexing, vibration). They are widely used in military, medical, avionics, automotive applications. Not strictly necessary for your application, but would certainly eliminate some risk.
Hope you will not develop a capacitor phobia, likely you just got unlucky and it happens.