Non Technical Question: FogBugz vs RT

Internally I am trying to get my company to use RT as our Customer
Support Ticketing system. There has been some pushback from management
as we currently use FogBugz as our bug tracking system and they would
prefer we stick to the same system for our support ticketing as well.
I have tried to explain my opinion on the advantages and disadvantages
of having these as seperate systems and the differences between the
two applications however I would really appreciate some outside proof
points that I can use in this battle as well.

Any thoughts/opinions/experiences provided are greatly appreciated.