Mesquite, Hickory, and alder are good for someone as a gift.
There is a great variation in their smoking characteristics, and can be mixed to get a creative taste to different types of meat, poultry and game.
We use these primarily.
It should be noted that although I can't speak for the Traeger brand pellets, most good pellets are nothing more than 100% pure wood that are simply milled and then compressed under high pressure to form the pellet. No additives need be added, but I'm sure cheaper pellets could be blends of cheaper substances as binders along with real wood. Check when you buy.
Why do we use pellets, simple, you can get all the advantages of wood with a very accurate way of getting the smoke to the meat. Pellets allow you to control very carefully when , how long and with how much smoke you apply. They are also easily blended accurately to insure you make consistant product.
It really is annoying when you see wanna be's that think they know it all about something make generalized statements like some of the above. Pellets in a lot of cases are nothing more than 100% wood period.
So I think its a good idea to give your friend a variation to try, and encourage him to weigh and blend them, as he may find a nice combination that will go well with a certain type of meat.
Home and commercial BBQ couldn't be further from this competition crap that everyone seems to hold in high esteem. It's designed to try and sell someone that may not even be qualified to say this one is better than that one with nothing but one bite and a couple overrated tests on how it should break apart. I know some that won't eat or produce what they'd cook for a competition. I've never been impressed by that facet of BBQ, nor do I see it anything other than it is, a profession or hobby onto itself.