Thank you for the thoughtful replies.

I have a 1993 300SL with the the four piston setup, and a 1995 E300D with the two piston floating caliper design. And it just seems to me that for the W124 cars with the diesel engines, the stock brakes are on the weak side compared their higher performance siblings. Maybe due to the heavy diesel engine...

After 292K miles it's time for a new master cylinder. Was just wondering if it would be an upgrade to use the 1" piston instead of the 15/16". But w/o changing the calipers (and disks + wheels to go with it), it looks like maybe not much of an improvement.