Exhausts aside,
I suppose what some don't care for in the 60x engines, is the fact that they sound almost gasser-like in the upper-ranges of the engine's revolutions. They really scream bloody murder... And like it.
I remember the sound of the promotional German video of the C111 Gen 3 racing around the track at 200 + mph. That 617 engine was unmistakable.
I suppose the 617 fits the Mercedes best since it sounds like an older, more mature fellow (who's had a few cigs in his time), voicing over the engine speed range.
The 603 sounds like a teenager arguing his piece in a verbal debacle.
This is all, IMHO.
The gasser engines M119 = alto, And M104 = soprano. M103 = alto.
So, 603 = tenor 617 = base.....
And one more......OM603A (350SD/SDL) = Base.
