I've been using hickory wood chunks with Royal Oak lump charcoal to barbecue pork. Recently I tried some apple wood instead and noticed a big difference in the depth of the smoke ring in my pork butts. The apple wood seems to provide a deeper and more pronounced smoke ring. I used the same rub, the same charcoal, etc.
Besides the smoke ring, I observed that apple wood has a much milder flavor profile versus the hickory and I was dissapointed with the lack of smoke flavor in my pulled pork. Next time I'm going to try a 50/50 mix of hickory and apple chunks.