This is a tough question to answer as a PFE when I work with customers for whom, the release of both products came almost around the same timeframe. For many things, we rely on product groups to answer such questions and Exchange Team has answered it on their recent blog post.
I am sure there will be many more questions around this post. I am looking forward to reading interesting discussions that will follow.
On the lighter side of life, if you are getting ready to shoot someone for this issue, make sure that’s not me as I have nothing to do with how those decisions are made, neither do I have any input in that process. I’m just the messenger.