Why did you decide on a double barrel smoker?
If you ran a UDS you can use Charcoal for main fuel and heat and run whatever type wood chunks you want for smoke. You can get wood chunks from a variety of sources including mail order and a UDS is much more efficient.
I can't tell much difference in wood smoke except Hickory is a lil stronger and Mesquite is real strong and can get bitter. I use Oak and/or Hickory mostly.