My experience has been that diehards sit on the shelf too long, and are "stale" by the time they are sold, and that their construction is not good.
Interstate makes both the Optima, and the Mercedes branded batteries. Optima is a great battery, has many advantages, but can suffer from both not being able to use stock cables, and being too tall for the battery box in some instances.
As mentioned before, be sure you get the correct size battery with the correct amps ratings. This is especially critical with diesel engines that need the additional cranking amps.
When I bought my Mercedes, it came with a Mercedes battery that was too small for the application. I replaced it with an Interstate of the correct size. I would not buy a Mercedes branded battery unless I just wanted the Mercedes logo on it, and was willing to pay 30-50% more to get it...
Here's a tip on buying Interstate batteries that will save you money. Try to deal with a local Interstate distributor directly. Ask if the have any "blems", or "pre-installs". These batteries come with the same warranties, but can cost 30-50% less than the "normal" battery.