All of them are accurate from an operational standpoint, they just use different chemical and physical properties from the product that you are using. Titration is the most precise one since it involves chemically measuring the presence of components of the formula, but it is not suitable for being in the production floor because it requires some skills. You can easily get distracted but the other two methods are very precise and can control your process without a problem. So, all of them are good for controlling the process.