Addition: I think the maltsters are telling you more info with how they structure their product lines than you realize. When I say "light Munich", I mean the lightest color Munich malt that a German maltster sells. When I say "dark Munich", I mean the darker color Munich that a maltster sells. They aren't making products for their own benefit; they know brewers traditionally use these malts in different proportions in different beers. So I trust a proper German maltster to develop a good, rich flavor in their dark Munich malt since that's what German brewers would demand.
Don't pick by color. Pick German first, then select their darker Munich malt, then do some flavor tests to see which one you prefer. Then stick with it. You'll have to experiment in what proportions to use in different beers. I only use a little bit in an Oktoberfest, but can use a lot more in a doppelbock, and even more in a dunkel.
Look at the diastatic power of the grain to tell if it can convert itself (it needs to be above around 40). Decoction mashing can help with this conversion too, which is something people tend to forget.
If the flavor of a particular Dark Munich is too strong for you, try another maltster. Or cut it with Pilsner malt.
It takes a fair amount of trial and error to understand the flavor profile of the products you use, and then be able to visualize their contributions in different proportions in your finished beers. That's why I advocate using a limited number of malts and knowing them well. "Malts" means a specific malt from a specific maltster, not types of malt. Even with a known product, you'll see batch-to-batch and year-to-year variability. It's an agricultural product, so that's expected. Hopefully, maltsters can adjust their processes to give you consistency, but you have to allow for some differences.