I cannot personally answer any questions about a comparison because I've never driven an automatic 300E but I will tell you this:

Suginami comes to Dallas once or twice per year and we usually get some folks together for dinner. I pick him up at his Hotel and drive him to the event. Until recently he had an M104 engined 300E, and I might say an absolutely MINT copy. Every time I would give him a ride in my 5 speed he would remark about how the manual makes the car come alive and other comments about how fast it was.

His feeling was that my 103 engined car accelerated harder than his 104 engined automatic.

To me, it's not the acceleration that makes it so much fun to drive. I am a manual transmission fan and just don't like driving an automatic. I don't care if I'm in a terrible traffic snarl and move five feet every 30 seconds, I STILL love my sticks. The problem is that it makes my car selection quite limited and getting more limited. The 300E is a FABULOUS car with any transmission IMHO, but when you put a manual tranny in it, the car becomes a phenomenon AFAIC.

As an example of such limits of manual transmission production in the US, the latest generation Ford pickups only offer manuals in the six cylinder two wheel drive models. I was needing to replace my pickup which was a 78 F150 4X4 that I bought new. Once I learned that there were no more 4WD V8's available with a stick I decided to find a good used truck of the last generation that offered it. I'm glad I did. Maybe it will also last 27 years.

Also your comment about gas mileage. You might search for my post about my vacation I took in early October. I wrote in great detail about the automotive part of my trip as it applied to my 300E and fuel mileage. The car got 29.36 MPG average for the trip which included mountain driving.

Have a great day,