Herblore, in my opinion, is only good for getting the actual skill to 99 and getting the skill cape. If you're the type of guy that likes being in combat related skilling and playing mini-games, Turmoil is your choice.
herblore is really only super usefull at 96. Mainly because you can use overloads and then just use brews for food.
Because while you're overloaded, brews can raise your HP but won't lower anything esle.
Depends if you plan on getting herb for overloads since you do gwd.
But honestly both if you can cause turmoil plus overloads are beast.
But either way both are good and imo its pointless to have turmoils but no overloads and vica versa.