VAE and PVA, while interchangeable in some cases, are quite different in terms of cost modeling as well as their characteristics and uses. Due to their better capabilities in adhesion, flexibility and resistance to weather, VAE emulsions find use in construction as well as in adhesives. On the other hand PVA emulsions are much sought after because of their ability to form a film and dissolving in water which makes them ideal for use in textiles, paper and coatings. So, based on the needs of your task, you can select the cheapest of them without any deterioration in the quality.