thats really only a matter of if you want to spend alot.
It shouldn't be to costly with yews, since u can get bonus xp from the 2 items in the mini game, of course if u got inferno adze u could simple chop the yews ur self and go for wc and fm xp, would take alot longer but would be cheap and get both leveled.
I would go with yews after burning that many willows (which i know the feeling) just to finish.
but like anyone would say, if u want to save money go with mapels
You should also post how many of each would u need to get to 99 it tends to be helpful when looking for advice.