If I were to pick only ONE wood - it would be Apple.
However - I keep several types on-hand
You may also want to factor-in the type of Charcoal that you're using when selecting the type and amount of Smoke Wood that you use:
Some charcoals ALREADY have a certain amount of smoky flavor built-in (K-hickory, K-mesquite, regular K-Blue Bag)
In these cases - a few chunks of smoke wood is all that you need
Some charcoals are very "flavor-neutral" (I find Cowboy lump to be in this category) -
With these, you can really lay-on the smoke wood
As you get comfortable with cooking different meats on your WSM - you will also find that:
- Some meats are better with MORE / Stronger Smoke Wood (Pulled Pork / Shoulder)
- Some meats (Un-Brined Poultry) only need a little or sometimes none at all
MOST of the time - I like a "mix" of about 50% Hickory / 50% Apple.
(Too much Hickory imparts a "hammy" taste that can become over-powering.)
Experiment around - at first, I would try only one kind of wood at a time, and see what you like.
It's a learning process, and since everybody's "taster" is different - it IS NOT an exact science