The Super Connie seems to have been the faster of the 2 with a cruising speed normally in the range of 290-300 M.P.H.,whereas the DC-7C cruised at 255-260 M.P.H.
DC-7C had a max payload of 21,516 lbs (9,759 KGS),the Super Connie max was 18,300 lbs (8,300 KGS).
Connie Model 749 cruised at 327 M.P.H. with max payload of 16,300 lbs (7,395 KGS).Similar numbers for the DC-6A and B were 315 M.P.H. (both) and 28,188 lbs/12,785 KGS (A) and 24,565 lbs/11,142 KGS (B).
"Luck and superstition wins all the time"!