Both pieces of equipment have their place.And if used properly work quite well.How old is your horse and what do you use on her now.She may not be really broke.Just because a horse does't buck and get wild doesnt mean they are broke.Another thing could be her teeth if their is a problem then nothing will help untill you address that.Another thing is you may be pulling too much with a bit that pinches.A running martingale and a fork work simular.Every one in the horse training business uses one at one time or another.The thing most do not like about a fork is it can not be let out as far as a martingale and the pull on one is nearly straight down,works good on race horses though.With a martingale you can addjust it to where you can bend a horse farther with less restrection on them.A good ring snaffle and a martingale adjusted to just tuck the horse a little work pretty well.I don't use a tie down on one untill I just have to on roping or barrel horses.On riders I don't see they work well.And I never use one on a pasture horse.All this will be of no use if you don't check her theeth and if you pull too much on one.Another thing you can not train a fresh horse they need to be rode down and the edge rode off of them.Some take a lot and some not so much.Untill she drops her head and will lope a nice easy about a 30ft circle, on a loose rein and stop smooth and flat and easy stand still back a step or two,and stand still, and take a breath and lick their lips they are not ready.Just like I said every piece of equipment has a place if used properly.But mostly it is in your hands.