I shoot the E32 for hunting and E35 for 3D and backup bow, I have owned several other Elites as well. The Answer, GT500, and Envy. I have not shot the Synergy but I'm sure its a good shooter. Elite as a company has been great to deal with the very few times I have needed to. I had a cable slide paint coating wear down and I was even using a aftermarket slide that I think may have caused the issue. It started making a little noise during the draw so I called to purchase a new one and go back to the original slide. They sent me a new one FREE even after saying I think a aftermarket cable slide caused the issue and was cool paying for it. The tech guys have been super helpful and nice when I have had questions about tuning and bow setup(I started doing my own work). So yes Elite in my eyes stands behind there stuff and has an unbeatable warranty. Sorry not much to share about the Synergy specifically. Its between the two I own in size and a little slower in speed so I haven't had the desire to mess with one.
I have never owned a Hoyt, or shot any much at all. He should get whichever one he shoots and likes better. And if nothing else he should get the Elite just so you can have friendly bow rivalry with each other... haha. My hunting buddy shoots Mathews so you know we flick each other $#!* all the time.