Honestly, turning pro was the best option for Brady. NHL, AHL experience would be ideal but I'm sure his bro raved about his time in London too so all options are good.
He heavily consulted both his father Keith and Matthew on the best course to take and those two are invaluable resources at his disposal to help him carve out a successful NHL career (or just to ask for advice). In fact, he even mentioned having talked to Matt about what it took for him to enter the NHL and stay as a top 6 forward during this teenage rookie season.
Also, having Logan Brown, his childhood best friend, which whom he played with before, is also a great asset. He's a friend, there's chemistry between them and most importantly Brown is a play making center, which would compliment Brady's game a lot. A line of Tkachuk - Brown - White (all USA line) will be amazing to watch in the near future because I think their styles compliment each other well. Even though Tkachuk/White aren't known for their offense, that's where having a center like Brown as the set up man so important.
It just sucks that he'll be compared to what Matthew accomplished and if he doesn't reach that within his first couple of seasons people will be calling him a bust etc when in reality, he's exactly what the Sens need (even though I really wanted Zadina and was initially pissed at the draft).