Though I am skeptical of the bad rep MSG gets, I find that I can get the same umami flavor for the most part from using nutritional yeast. I like the fact that it gives me control over the umami aspect of what I'm cooking without altering the salt content. That let's me control the saltiness of the food with actual salt rather than adding MSG and hoping I'm not oversalting for the sake of having that "secret sauce" effect MSG imparts.
I have no idea if it's truly healthier than MSG (the claims on both substances are many and varied, both heavily skewed by questionable research), but it's a great ingredient to cook with.
(Full disclosure, I'm not a vegetarian/vegan, so no bias there. I know nutritional yeast is usually tied to that group, but I'm just a person who likes cooking with just about everything I can get my hands on.)
I find nutritional yeast tastes cheesy. It's just not the same as MSG. I also find that MSG goes a long way... just a dash in an entire casserole can elevate the taste without going into salty territory.
By themselves, they definitely do not have a 1-1 taste. But if you put MSG and yeast in a dish where they are well integrated (such as the casserole you mentioned) and evened out the salt, I'd be hard pressed to tell you which is which.
I use a mix of porcini/shiitake/maitake powders, nutritional yeast, MSG, stock bases (with their hydrolized proteins), fish sauce, soy sauce, Vietnamese mushroom seasoning, and Worcestershire sauce to control my umami, and they all have their specific uses. Nutritional yeast and fish sauce are the most likely NOT to go with the flavors of whatever I'm cooking, and MSG can literally go into anything as long as I know I want to use it prior to doing the final salt edit.
I have no idea if it's truly healthier than MSG (the claims on both substances are many and varied, both heavily skewed by questionable research), but it's a great ingredient to cook with.
(Full disclosure, I'm not a vegetarian/vegan, so no bias there. I know nutritional yeast is usually tied to that group, but I'm just a person who likes cooking with just about everything I can get my hands on.)