Yes, there's a WORLD of difference in driving a 124 car vs. a 123. After I started driving my 300E, I said I could never go back to driving a 123 on a daily basis. Now that some time has gone by though, I'm enjoying driving my daughter's 300D. They're just different animals.
I did notice the firm brake pedal on the 123 car when I started driving it. I'm sure that there's nothing wrong with the brakes on my 300E, and I don't notice the pedal on it to be in any way objectionable. But when I get in the 123 I definitely notice a firm pedal.
Without pushing the pedal with my own foot, I don't know if your 300E is okay, or if you have air in your system. Was the pedal better before you did the brake work on the 300E?
It never hurts to do some more bleeding, it will just freshen the fluid that much more. Some cars have to have the power assist to get them bled properly, meaning engine running while bleeding. A pressure bleeder would eliminate the need to run the engine.