I think that if you really want to compare these two tools tehn you should try to get a demo copy of each (the local sales rep will most likely agree to this if you tell them why).
Define some cases that explores "the corners" of what you may work with and set each case up in the two tools.
Define your "acceptance criteria" up front - what is most important. Ease of use, simulation time, GUI, interface with other software tools, support desk efficiency (try to predine a "support case" and see how tehy respond) and so on.
These are pressy expensive tools, that also comes with an annual maintenance fee so you can justify some tiem spend here.
