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.
When I re-read the OP, I realized my faux pas. It wasn't my intent to merely feel out people's preferences on a single dimension, but more to get a feel for the cross-section of different approaches, and perhaps generate further discussion on the broad spectrum of approaches.
So, thanks for the thoughtful post Thomas.