I've got Flows (NX2-AT) and Rome Targa's, and I've been swapping them back and forth this season on my boards. Here's what I find:
Flows need to be set up properly. Until you get them dialed in, they're a PITA. Traditional bucklers, you just tighten until satisfied.
Once the Flows are set up properly, they are way more convenient when getting off the lift. You can snap in without even stopping once you get proficient.
I don't detect any difference in responsiveness going heelside. There may be a very light mushiness in Flows going toeside but I wouldn't swear to it.
If you're going to get Flows, get the NX2's if at all possible. The NX2 mechanism allows you to have the I-strap tighter when locked in.
FWIW, I'm an intermediate rider and only into park a little bit. For a high-end rider, there may be more of a difference.