The purpose behind 'the schema' is to help search engines better match semantic search terms with relevant user information. Word out there is that is doesn't help in the SERPs. See this article. But it might and Google may have integrated it into their algo yesterday for all we know.
With it being relatively new in the search landscape and little evidence of testing out there, I'd recommend that you donate some time to the cause 
It just so happens that you'll likely get your answer from doing so. Here's how I'd do it:
1. Choose the pages you'll be measuring... the more you use, the better the data...
2. Measure where these pages rank in your search results before making any changes.
3.. Divide those pages into thirds and apply the 'Events' schema to a third, the 'Aggregate Rating' to a third, and apply nothing to the remaining third.
4. Track and report your findings.
Obviously, there are some potential hang-ups here (ie. if you aren't ranking in the top 50 for your target keywords and are using SEOMoz to track). After rubbing my magic 8-ball, I'm going to prophesize that you won't see a significant difference for a few reasons (or any at all).
Finally, I'd suggest that you persuade the engines to focus on the aggregate review information. If you look around, you'll notice that reviews are being increasingly integrated as major indicators in search algos. Events? Not so much.
There are many issues at hand, but you get to decide which are important and which you're going to act on. Either way, good luck!
