Mage::getModel() 将始终为给定模型返回一个新对象:

Mage::getModel() will always return a new Object for the given model:

/**
 * Retrieve model object
 *
 * @link    Mage_Core_Model_Config::getModelInstance
 * @param   string $modelClass
 * @param   array|object $arguments
 * @return  Mage_Core_Model_Abstract|false
 */
public static function getModel($modelClass = '', $arguments = array())
{
    return self::getConfig()->getModelInstance($modelClass, $arguments);
}

Mage::getSingleton() 将检查给定模型的对象是否已经存在，如果存在则返回.如果它不存在，它将创建一个给定模型的新对象，并将其放入已存在的注册表中.下一次调用不会返回新对象，而是返回现有对象:

Mage::getSingleton() will check whether the Object of the given model already exists and return that if it does. If it doesn't exist, it will create a new object of the given model and put in registry that it already exists. Next call will not return a new object but the existing one:

/**
 * Retrieve model object singleton
 *
 * @param   string $modelClass
 * @param   array $arguments
 * @return  Mage_Core_Model_Abstract
 */
public static function getSingleton($modelClass='', array $arguments=array())
{
    $registryKey = '_singleton/'.$modelClass;
    if (!self::registry($registryKey)) {
        self::register($registryKey, self::getModel($modelClass, $arguments));
    }
    return self::registry($registryKey);
}

在您的情况下，您总是想要一个全新的 Product 对象/模型，因为每个产品都是独一无二的...

In your case you always want a completely new Product object/model since every product is unique...