I would vote for the 93 300E. I am biased because I own one, but I feel the power is more than adequate. The M104 engine has terrific horsepower (217) and Torque (229), with a very flat and broad power curve. I have never felt that it was underpowered. Ever.
I wouldn't presuade you to avoid the V8. Horsepower is great. It's a reliable engine. I'm sure you've read all the threads about timing chain failures, guide rails, etc.
I have read reviews in the automotive press about the V8 W124's, and while they applauded the horsepower, I have read criticism about the extra weight over the front wheels and poorer handling (oversteer). However, with regular driving, I don't think any of us would notice that much of a difference.
In summary, if you think the M104 300E/E320 is underpowered, you need a whole in your head.
If you buy the V8, you'll have marginally higher maintenance and fuel costs, and the ridiculous need (to me) of changing the timing chain / guide rails, etc every 100,000 miles.
If you buy the inline 6, you'll have marginally lower maintenance and fuel costs (I average 20.5 mpg). However, if the engine wiring harness hasn't been replaced, change it immediately (about $800.00 installed). Head gaskets leak after about 100,000 miles, but can be ignored until the leak becomes too great. Mine started leaking at 130,000 miles, and it is a very slow leak. I've also read posts by Benzmac regarding engine fault code issues, particularly relating to low EGR flow. I had this problem, and the fix is posted on this site.
Why not buy the 93 300E? The asking price is $1,400 less and has about 40% less mileage.
2001 E430, Bourdeaux Red, Oyster interior.
1973 280SE 4.5, 170,000 miles. 568 Signal Red, Black MB Tex. "The Red Baron".