I dont inject chicken; grilled chicken doesnt need injecting IMHO...
Pulled pork, I do inject, but I stick to my own personalization of apple juice, worchestershire, and some of rub...
Beef, I think most who inject use their favorite of Kosmos, Butchers, and/or FAB. I haven't tried FAB. I prefer Butchers over Kosmos, but that has more to do with which one goes better with my rub...
You'll want to settle on a rub, then try the different injections with it to see which goes best. Also, for me, we found that they can get more than a bit salty. Also, I didnt care for them mixed with beef broth. I use the injection watered down more than the recipe calls for, and leave it out to "set up" overnight before injecting...