Rather than "hard" v. "soft" approaches, I prefer to look at it as management of tension across the full spectrum from soft-as-cotton to tight-as-testicles-caught-in-a-workbench-clamp. The successful training approaches that I've seen embrace that full range. For example, Aunkai methods build with high degrees of tension in specific areas (e.g., identifying and maintaining the sense of juji in the upper body), then back off the tension as basic conditioning improves the connection. Dan Harden works with specific exercises, including partner work, that can be performed with varying degrees of tension (from soft to very hard), depending on the purpose. This just reflects my very limited experience and understanding to date.
So how do you ever really train the real Qi/Ki if you do some hard, some soft? Don't you wind up with some (sure it can be strong, but that's not the Full Banana) muscle-based jin?