Having cooked on all types of cookers ranging from an electric smoker to offset smokers to kamados and pellet grills, I will say that each cooker I've cooked on gets you a different end result but they ALL DO get you there. The devil is in the details, much as Tee eluded to. My Smokin'-It smoker, for example, only smoldered the wood as it is an electric smoker, no fire ever occurring, but it still gave me smoked meat with a nice bark. I think a properly cooked piece of protein on a offset cooker (stick burner) does make a different tasting product, not necessarily better, and it is REAL easy to over smoke and get that bad acrid tasting smoke whereas I've never gotten that on a pellet grill/smoker.
Now, with that out of the way and back to your original post. I think although pellets are wood, they burn differently because they are cleaner wood than an actual log would be. Maybe the inconsistency with splits is part of the equation. Different seasoned levels (some too dry, some too green, some just right), bark, etc.
I'm sure others can extrapolate on this further but this is a very good topic! I look forward to my BBQ brothers and sisters chiming in.