I drove a 94 E420 Saturday for the first time. Those extra few cylinders REALLY make a difference.
IMHO if you get a used W124 in reasonable condition, with price reflective of the condition, you will be very pleased after making whatever repairs are needed. I would love to get hold of a cosmetically needy E class for a steal and spend a few weekends sprucing it up. Once you have ascertained that there are no major problems like A/C, transmission, oil leaks, wiring harness, the rest of the repairs seem to be fairly inexpensive and with the help of the pros on the website, fairly straightforward.
If you can get that 420 for a good price, jump on it.