In my experience, most coffee flavors and other dark e-liquids tend to gunk up wicks and coils so there's definitely a trade-off.
Taste is subjective and YMMV but I highly recommend trying
Java the Hut from The Vapor Hut.
My taste buds have found it to be a very precise, rich, coffee flavor and the bonus is you can order it "straight" or add up to two flavor shots (hazelnut, vanilla, caramel, Sin-a-Bon, and cream) to each bottle. I keep a minimum of 60ml with a single shot of cream on-hand at all times.
With the exception of their Abstract Clouds line, all TVH e-liquids are $0.50 per ml, regardless of the bottle size so you get tasty, complex flavors at a great price without sacrificing quality or consistency.
Wookey Cookie, Sin-a-Bon, and Big Papa-paya are a couple of my other TVH ADVs.
Good luck in your coffee quest!