Sorry... out of town for a few days.

The M-B parts are generally more expensive. Not always, though, since S90 parts are pricey in and of themselves, for some things. I've noticed that exhaust parts are expensive for the Benz, but things like some other parts (brakes and other standard things) are not so bad because they are somewhat standard.

I have to say, I am not up to speed on which years and models had what engine, for the 300 class Benz. I am partial to the inline 2.6 and 3.0 especially. I generally avoid diesels because you never really know how they were treated. The 4L and 5L (E400/E500) have a ton of power but I've never worked on one. The forum you cited would probably have much better information than I would have on that. there were some engine options (400 and 500 series "E" class) and there may have been a change to the inline six in the later years of that model (1995? or somewhere in there) but I'm not certain. I'm sure someone here owns one of the later models and could comment more accurately.

With all of the premium RWD sedans, be it Volvo, BMW, Mercedes, or Lexus, parts and service come at premium prices. It is my personal opinion that the LS400 is excellent, but the 6cyl E-class and S90 are both good cars. I think the S90 has gotten a bad rap in part because it has an interference engine design. Still it is a solid car, and if treated properly it should last for a while. Plus of course, it is a VOlvo so there is some familiarity involved. A lot of parts are much different than the 940 though (interior, electronics, engine/trans) so the interchange is very minimal. Some brake parts interchange. The rest of it is much different. But if you're not afraid to take on the complexity, it should be OK.

The M-B is not so bad to service. A lot of room in the engine compartment anyway. A solid car, good engine, familiar Bosch ABS, etc. The LS400 is a little more complex, a lot of things are a little bit on the "buried" side. It isn't geared towards owner-servicing. But a fine car nonetheless... and not in need of a whole lot of servicing in the first place.