I don't know if one is better than the other Lola. I went with the egg yolk lecithin partly for price, it is less expensive to use, because a bottle of it lasts so much longer. And I liked the theory better, that it emulsifies the fat helping the fur stay loose so it will pass the way it is supposed to.
Plus I don't like to use too much psyllium (bulk forming fiber) on a daily basis. I do use the Vets-Best daily, for incentive, mostly to cover the calcium/taurine/B powder on their PMR meal, then a little more over any supplement powder left in the dish, to encourage them to lick it all up. But the amounts, used that way, are very small, less than half a tablet between 3 cats.
The product is perfectly safe, you may remember the time TC OD'd on it, with no ill effects. (that cat has the digestion of a goat anyway, LOL). So if it is working, why fix it? On the other hand, like anything maybe it is good to alternate methods?
As far as I'm concerned ANYthing is better that those awful petroleum products. I can't believe I used them and believed in them for so many years, how could I not realize, hello, petroleum is TOXIC to ingest?