Had LS400 for couple of days as I sold it to ma cousin(who installed a CNG in it) and had driven many mercs as grandpa nd his bro have almost every model.
I steered LS400 on comparitively rough terrain and its response was just too gudd much better then the new C Class. Its damn reliable coz I tried to kinda offroad in it on ma way to Goth nd it ain't broke.
Newer models of Merc r not tht good since 98 onwards. Older models wer damn tough such as 280SEL(1986), one of ma favourite.
Lexus is a better car then a C-Class or E-200 but unfortunately Lexus don have tht glamour of Merc, I am talkin in local scenario.
As far as reliability is concerned in our part of the world, ther is always a car piloting a Merc ir whenever it breaks down he can giv a call to his home nd ask the driver to pick him upp.
If, I will to choose between a Merc nd a Lexus. I will always go for a Merc.