My 280 SL had an ANSA rear muffler when I bought the car 8 years ago. I have a friend with the stock system on his 280 SL. The ANSA exhaust is certainly raspier, especially when you are on the accelerator. It makes for great noises when you are cruising with the top down. For a little fun, it is great to punch it when going under an overpass and hear the reverberations. The stock system is quite civilizee in comparison. I don't thing the ANSA system is excessively loud but certainly is sporty. Which is also appropriate as I compare it to the sound of my '63 220SE's exhaust note. I live in a relativey humid climate. I usually drive the car once every two to three weeks and usually drive 5 to 10 miles between stops and starts. I haven't had any problem with muffler rust through during my ownership, and, as I said previously, it wasn't a new muffler when I bought the car. I hope this helps.
1969 280SL, manual, MB TEX, green/cognac