I use only Monin... Have tried Ghirardelli and Torani, but so far the best is Monin Dark Chocolate so I doubt I'll look any further than that. Has a very natural taste without the chalkiness usually found in others. Also cost effective as you typically use less per drink...
Also going to make the switch to Monin Caramel and White Chocolate sauces, as well as slowly switching to their syrups. Not as sweet as other brands, but very bold in flavor profile as well as tasting natural, whereas most brands simply don't. Later!
Make our own using a combo of dark chocolate chips (melted down), Ghirardelli powder, vanilla and almond extracts and some powdered sugar.