160?! How tall are you? Anyway id say the Unions are the way to go. The flow bindings, in my opinion, dont have the reponse you would want for park. Take your boots to a shred shop and click into some binders. You'll be able to tell if you like the pressure points in each binding.
His height plays a small role in board size. Even then, at 210lbs, 165 is on the long side.
If you use a wide board, I'm guessing you have size 12 or 13 boots. You'll more than likely require XL bindings. The Flows are great for comfort, but as Ninja stated, it's not the best for park. They do take getting used to. I'll even be as bold as to say you'll likely downright hate them the first couple of laps.
Personally, I love my Flow NXT-FSE's. However, I don't jib at all. I do all-mountain freestyle. It's great for that purpose. Stomping out landings on these feel great. Traditional straps do offer a bit more response, but it's nothing significant enough for me to avoid Flows. The comfort and speed of entry far outweigh the difference in response. If you want something more flexy, the ATSE are slightly less stiff.
I do recommend that you contact Flow for extra hardware if you get their bindings. It's always good to have spare parts for it in your bag. Not because they break easily (I personally have never had an issue in 6 years), but because parts can be hard to come by when you are on the mountain and in need of it.