I'm waiting for my Pitts & Spitts Maverick 850 to arrive, and I'm aware that many say pellet smokers are a bit short on delivering the smoke flavor; but here's what I DO know. In the world of "strong," mesquite and hickory are the top two. I've always used in order of preference, oak, apple, and cherry. If I find that a brisket at 250F for 12 hours or so comes up short on smoke flavor using only oak; then I'll mix in no more than 25% hickory or mesquite to oak for starters and increase if necessary as needed.
Hickory and mesquite are STRONG; but if pellet smokers are lacking in their ability to impart smoke flavor to the cook; then I'll increase the ratio until I'm where I want to be. FWIW; I've always been a strong proponent of straight oak. I'm with Aaron Franklin in that view.
I'll report back.