This probably isn't the answer you were looking for, but given customer constraints (their budget, tastes), I try to design what'll look best with the scape: stone, brick, trench, black poly, aluminum, wood. They're all workable, and 'most pleasing' depends on the design to be used.
I like to use trenches around berms..Makes for easy maintenance..Pretty much cut all trimmer work when mowing..I usually just outline the beds and trench around them with old fashioned elbow grease..(shovel and mattic)..Clean-Cut
I present all options to cutomer and then work with their preference and pocketbook. However, I personally prefer stone set on edge in a trench with mortar and re-bar tying all together. Works great in high traffic areas and will last forever...or until new owner decides to rip out and put in plastic, ugh!
We use all of the above types of edging. It depends on the type of landscape that it will be going in. Cost is another issue. Black diamond edging and natural edging is the most popular and cost effective. There is also an excellent profit with these. If you have a trenchmaster it is really fast work.