Bah! While some of you were busy posting, I was busy calculating! 😉
The following is based on info I've collected about the ECCp client. Not the latest client, but considering the data on TA.com for RC5 and OGR probably isn't exactly 'fresh', it probably won't matter anyway.
ECCp vs. RC5
Better at ECCp
K6-3..........................0.812
K6-2..........................0.860
Athlon TBird/Duron...0.909
Athlon Classic...........0.929
P4.............................0.954
PPro/P2/P3/Celeron..1.009
Pentium Classic.........1.123
Pentium MMX.............1.404
Better at RC5
ECCp vs. OGR
Better at ECCp
Athlon Classic............0.761
Athlon TBird/Duron....0.793
PPro/P2/P3/Celeron..0.911
P4.............................0.984
Pentium MMX............1.028
Pentium Classic.........1.146
K6-3..........................1.154
K6-2..........................1.223
Better at OGR
Edit:
In case some of you would like the ECCp rate data, in [it/sec/MHz]:
Pentium Classic = 200
Pentium MMX = 240
PPro/P2/P3/Celeron = 445
P4 = 227
K6-2 = 317
K6-3 = 336
Athlon Classic =587
Athlon TBird/Duron = 600
Athlon Palomino/Morgan =600