I don't think you could make a bad decision here. Your project is big enough and unique enough that any bug fixes will be very small in compairison to your main task. You will have more issues with the actual way things work, than you will with the way they don't work. The good news is that with either choice you can change the way any part works. A simple example is the templating system. aD correctly resisted the temptation to create more tags. However they are easy to add. More annoying to me was the functioning of the master tag, which takes a source (src) argument. The implimentation doesn't allow you to specify an absolute path.
Only thing is to not underestimate the last 6-9 months of work by some very experienced developers, who have not only ported the code to another database, but have actually done some serious bug fixes that will never show up until you get real data in the system.
My opinion would be to take the core, either one, and do the rest by hand, unless there is a very close fit with a particular module.
