CRV 2014 exhaust noise and bad rear drive shaft
 

I thought Honda last a long time but just over 8 years and 65k miles I have to replace the rear drive shaft. It is rusty and the mechanic says it will make a noise soon. There is also an exhaust noise when accelerate, that noise last for a few seconds and then disappears. I took the car to two shops but no one knows where the noise comes from. It sounds like a bad muffler noise but it come from the front/driver side. Doe anyone experience similar problems?
Questions: The two shops offer me two different rear drive shaft; Precision for about $1100 including labor and shipping, the other shop offers Dorman for 1575 including labor and shipping. Which brand should I go for?

Why is the shaft needing replacement, just rust?
A picture might help but 'make noise soon' doesn't say a whole lot.