Naturally it would depend on how the final product turned out but I would say yes that I would use the open source tool. One of the annoying I've always found about EM is that I'm never sure exactly *how* it does things. It would be great to have the source code available to pick through.
Another thing I've always wanted EM to do is have an option to record everything you do through the manager. i.e. a script builder
I "grew up" on GUIs and tend to do my thinking, planning and testing there. It would be great to be recording everything I do so that I could then go back and use that script as a starting point for the changes to the production database.
"I met Larry Niven at ConClave 27...AND I fixed his computer. How cool is that?"
(Memoirs of a geek)