Fillet string everytime. Hate legs straps with a passion as have seen horses tangled up in ill fitting ones plus I always foget to undo them when taking the rugs off.
totally agree, leg straps are there for a good reason!!
Most of mine wriggle out of a rug without leg straps on, fillet is ok for night but wouldnt turn out in a field with just that on unless it was loose summer sheet etc.
I don't like leg straps but have found with my new mare, who has a very long back, that with cross surcingles and a fillet string, the rug slips to one side, whereas on my pony, I've taken the leg straps off all her rugs and they never slip. So I guess it depends on the shape of the horse.
As mine mostly live out I always feel vulnerable putting the leg straps on when out in the field. That's the reason why I've ditched the 'spider' on one of my rugs and swapped to leg straps and had X surcingles sewn on because putting a spider on 'in field' is highly dangerous with an excitable horse!