I don't know how much a M-B muffler will cost, but I'll bet it will last as long as the OE muffler. If I read your signature right, another 223k miles or so...
I'd go for the M-B part. I chased OE parts for the Suburban a few years back and the local garage who installed it said OE fit better than any other replacement they had used.
'96 E300D 60k mi (wife's daily ride)
'95 Audi 90 118k mi (for sale)
'92 GMC Suburban 138k mi
'85 300SD 231k mi (my daily ride)