In most recipes involving whipped egg whites or whipped cream, you are instructed to fold a the whipped mixture in parts (thirds) into the non-whipped mixture using a spatula. For example, angel food cake or souffle.
But, it is easy to deflate the mixture too much when using a spatula, especially for someone inexperienced, so why not use a whisk? Other than scraping the sides/bottom of the bowl, I don't see any reason why you shouldn't, and you could also use a folding motion while also preventing the mixture from deflating, and combines them faster. Personally, I prefer a whisk.
Is there any other reason to use a spatula over a whisk, or is it just conventional practice?
In other words, is convention correct (based off your experiences)?