I find a mix of absoprtion and diffusion works best. You really have to experiment to achieve the right mix and the effect you desire. Diffusion would decrease and spread out specular reflection and make the room sound bigger.
With mostly absorption, the sound in my room was very focused but I was always aware of the side boundaries. The diffusors along the side and front wall increased the perceived width and depth of the soundstage and relieved a lot of combfiltering problems at mid and high frequencies. The traps or absorption was not as effective as the diffusors at the upper frequencies.
When I had too much diffusion along the frontwall, the soundstage was too far away and individual instrument lost focus. It is really up to you to decide whether you want a large hall sound vs small Jazz venue. Good luck.
With mostly absorption, the sound in my room was very focused but I was always aware of the side boundaries. The diffusors along the side and front wall increased the perceived width and depth of the soundstage and relieved a lot of combfiltering problems at mid and high frequencies. The traps or absorption was not as effective as the diffusors at the upper frequencies.
When I had too much diffusion along the frontwall, the soundstage was too far away and individual instrument lost focus. It is really up to you to decide whether you want a large hall sound vs small Jazz venue. Good luck.