Well,

I didn't like Reunion so much that I stop using it. The most obvious advantage FTM has over Reunion is being able to important information directly in from Ancestry.com. If you have done most of your work in Ancestry than that is what makes it more attractive.

I received help merging family trees. That was a headache but after speaking with someone at Ancestry.com, I figured it out. It is a matter of attaching a person to a family after the merge has taken place.

I think being about to print various family trees in FTM is a great advantage over Reunion.

I still have more to explore.