1298 .... if you want low maintenance and the thrill of driving a german machine go for the benz. There are some mods you can do but mostly they are cosmetics, sport rim, bodykit and interior. Engine mod wise, not much option. I have friends driving late 80s E classes and don't bring problems at all. Still in it's prestine condition, some lowered and some with nice AMG/Carlsson rims. But do remember that the 300 comes with a RM2000 road tax. Mercedes has the BEST turning radius among all cars.
BMW however is a pure driver's car, even though it is 10 or 20 year old. They don't call it ultimate driving machine for nothing. It does however come with high maintenance but if you apply some TLC, it will not give you much problem. When it's time to change some of the parts and it's regular oil change ... you better do it. You can find some reliable BMW mechanics around and some of the parts you can actually buy it your sell at some of the parts shop. Don't have to pay a bomb. :)