I use Sigma Aldrich agar, I also used them for a lot of my chemicals as they have great quality. The agar though isn’t really that important as I’ve used the stuff out of bulk bins at a whole food store and had little to now issues. The base of the media depends what your doing. If your isolating, then yes it would be vastly dependent on whats in your media. For instance if you were trying to get yeast out of a culture that has bacteria in it, you’d use a media that contains chloramphenicol which is a anti biotic. If you were looking to get the bacteria then you’d use cycloheximide to kill of the yeast. So on and so on. But if your just looking to prop something up the the environment doesn’t really impact the flavor of that short of a growth generation. But you’d still want it to be an optimal environment for them to grow in just for the sake of vitality.