Generally, OS X 10.5.5 did not move the benchmark scores much. The big changes occurred with 10.5.1 and 10.5.2. Even though 10.5.5 was supposed to include changes to the graphics files, none of the graphics tests showed much change. Maybe with other Mac models but not with my white Core 2 Duo iMac.
Here are my Xbench scores for 10.4.10, 10.5.0, 10.5.1, 10.5.2, 10.5.3, 10.5.4, and 10.5.5. (10.5.2 thru 10.5.5 after running Xupport optimization routines)
Overall: 113.91 120.40 124.76 124.21 126.06 126.19 124.88
CPU Test: 111.50 125.42 124.39 135.20 134.98 136.15 136.24
Thread Test: 217.12 180.96 180.88 197.29 200.76 196.76 185.63
Memory Test: 124.02 137.88 138.99 138.36 131.00 140.75 138.65
Quartz Graphics Test: 141.15 171.07 173.21 174.44 171.67 169.26 174.35
OpenGL Graphics Test: 193.92 210.66 221.00 194.67 219.46 215.24 211.10
User Interface Test: 385.19 260.99 304.65 302.85 273.40 293.84
Disk Test: 40.04 43.54 45.95 44.46 45.91 46.02 44.97
Here are my Xbench scores for 10.4.10, 10.5.0, 10.5.1, 10.5.2, 10.5.3, 10.5.4, and 10.5.5. (10.5.2 thru 10.5.5 after running Xupport optimization routines)
Overall: 113.91 120.40 124.76 124.21 126.06 126.19 124.88
CPU Test: 111.50 125.42 124.39 135.20 134.98 136.15 136.24
Thread Test: 217.12 180.96 180.88 197.29 200.76 196.76 185.63
Memory Test: 124.02 137.88 138.99 138.36 131.00 140.75 138.65
Quartz Graphics Test: 141.15 171.07 173.21 174.44 171.67 169.26 174.35
OpenGL Graphics Test: 193.92 210.66 221.00 194.67 219.46 215.24 211.10
User Interface Test: 385.19 260.99 304.65 302.85 273.40 293.84
Disk Test: 40.04 43.54 45.95 44.46 45.91 46.02 44.97