Originally Posted by
hokiefyd
Mountain components are generally not any more durable than road components. Traditional mountain derailleurs (like the RD-M360 you just bought) don't have stronger springs to eliminate chain bounce (often called chain slap), but Shadow-style derailleurs do have much stronger springs. Many also have clutches. But this isn't only mountain derailleurs anymore -- many of the road groups are moving to the Shadow-style design, both with and without clutches (this is talking only of Shimano, here). There generally isn't a difference in shift precision between road and mountain derailleurs at the same "quality level" but I imagine that function improves in both lines as you move up in price.
Your bike shop is correct that the M360 will work with your Acera shifter. This is most applicable if you're trying to use indexed shifting. If you're shifting with a friction shifter, then the distinction between "mountain" and "road" pretty much goes away.
The more people talk about it the more they say how much the Mountain Bike Derailleiurs and Road Bike Derailleurs are alike. Yet they are designated Mountain Bike Derailleurs and Road Bike Deraailleurs. I thought something had to set them apart. I thought it was sturdiness. But that is not it.
What is the Shadow Design and how does a Clutch work in a Rear Derailleur?
My Acera Shifter is index and the product description from Shimano said the M360 Acera Derailleur shifts quickly and crisply especially with the Acera Shifter. That is why I bought the Acera Derailleur. I understand the Acera is a slight step up from the Tourney and it was only $25 on Amazon. I do not know what the Bike Shop will charge me.