Am I just unlucky?

Things like this can happen, even with top quality gear.  Some units can be on the shelf for quit a long period of time before they are sold.  Some capacitors cam become deformed during this down time.  It is better to allow the new units to reform by starting the up for half an hour with out firing and then proceed to flash and needed.  This may not be the case, however, and the unit that exploded may have been a lemon to start with.   

When you send the units back to B&H ask them to test the units before shipping the new ones before sending them to you. The don't have to do a complete work up on them- just a test to see that the units don't explode and that the proper screens come up when they are used in conjunction with each other. 

I have seen, in the past, when flash units have basic engineering flaws or bad components on a global basis.  I have not seen or heard of this lately- so it is probably a matter of happenstance.

When it comes to electronic flash in general, I am kind of an old school guy.  I like the big and tough and relatively unsophisticated.  The more bells and whistles, as far as my experience goes, the more potential for failure, especially in the wedding business where there are long duty cycles and a rough and tumble situation, as far as delicate circuitry is concerned.  On the other hand, the gear that is dedicated to your camera may work like a charm.  I don't know exactly what the units you mention can do as far as long hours of service and how well that stand up to heavy duty use.

I hope this helps.  Ed Shapiro