My father ownes the Lexus, I own the Benz, I repair both. Both of our cars has been very reliable, with expensise slightly higher for the Benz (it needed some A/C work last summer). The Lexus has run really reliably.
As a daily driver both are quite comfortable. The engine in the Lexus revs really freely to high rpm's, and the sound system is out of this world. The Benz motor seems 'tighter', less able to rev, but has really good torque. Both transmissions shift really smoothly- although at different RPM's.
If I had to choose I would buy the Benz again, it's just so well put together, and the materials used are much nicer.
I hope this helps.
1995 E320 40K
1999 Tahoe 90K
2002 JX8 Sport 43K
2005 Volvo s40 65K