I’ve run a bit of an experiment in my garden with this, 3 beds… 1 with manure at bottom and compost top layer, 1 with seaweed compost on the bottom and a general compost on top, and one with a john-innes type compost and general compost on top.
Still early days (done in September) but I’m seeing good growth in all beds – so can’t tell them apart. The biggest difference I’ve seen is when watering – the john-innes bed the water tends to run a bit before soaking in.