My personal preference is bark chippings. I use bags from Wicks since the quality is much better than B&Q in my humble opinion.
This year's order is 18 bags because I skipped on bark last year almost completely and I'm doing everything this year.
I use it for a few reasons but mainly because my compost doesn't cover the ground I need to protect and it degrades into the soil to become a wonderful loam, given time. It does dry out a bit in the summer months, but I always apply thinkly and dream of the loamy goodness beneath. It leaves me very little weeding to do over the year and looks great against the plants, just try to use border edging, or it can look messy.
For some specific plants such as hostas, I incorporate my own compost in early spring, then top dress with grit to keep the slugs off, a circle as far as the leaves spread.
I covered a border last year with bark chips and am about to start preparing the bed for planting (lavender). Should I remove all the old bark chips as well as stones or can I be a bit more relxed about it?
Thanks v much.