I´m talking performance, reliability, comfort, durability, etc...

I have driven both.

Mercedes-Comfort
BMW-Performance, reliability.

But both feel slow because they both have quiet and smooth rides so you don't really hear the engine or feel the acceleration.

Neither. I would get a nice Hybrid or a SmartCar. If I had to, I would pick the BMW. Mercedes are not good cars.

why dont u try Aston Martin V8 Vantage

Performance

Max speed: 180mph (290 km/h)
Acceleration: 0-60mph 4.7 seconds
0-100km/h (62mph) 4.8 seconds
Max power: 313kW (420bhp) @ 7000 rpm
Max torque: 470 Nm (346 lb.ft) @ 5750 rpm