My experience with the Optima battery have been very positive. After having 1 VW factory battery explode and the replacement crack and leak all over, I did some research and decided on the Optima.
Granted, both the MB and my VW are diesels, one of the factors in deciding on the Optima was their vibration resistance and deep cycle capabilities. They are sealed and have a special spiral-cell design that makes them almost bullet-proof.
I found mine locally for around $125, which may or may not be a great deal...so when the time comes for a replacement for the MB battery, it will be an Optima.
Just my $0.02.
Sold: 1987 MB 300SDL, 320k miles, Astral Silver, Blue Leather, all books and records from day one.
Totalled: 1998 VW Jetta TDI, 488k miles, Classic Green/Gray Leather, loaded, E-Codes, "Slightly" modded, "Slightly" faster than stock, arrived 11/07/1997.
MBCA Member, Chicago Region