The 603 is 6gallons of engine in a 6 gallon bucket

The 617 is 5 gallons of engine in a 6 gallon bucket (the w126 body)

The 617 is easier to work on than a 603...hands down.

Less wires, less sensors, smaller engine, easier plugs, easy IP access (ALDA).

Its simple...smaller engine in same size bay is automatically easier to work on.

Now if you want to talk DESIGNS or engineering then thats a whole nother boat.

But ease of working on one or the other? 617 hands down. The less you got to work on and the simpler the design the easier.

Just my thoughts...you guys can argue about other stuff.