Thanks to everybody for the help. I finally completed the upgrade, having reinstalled the OS to get a GUID and reset the PRAM.
Boot up is now 28 seconds vs 30 seconds with the Apple SSD.
The XBench comparisons are still good:
runcore ssd vs apple ssd:
Overall = 153.13 vs 133.87
Disk Test = 195.62 vs 80.95
I'm no xbench expert, but the overall score does puzzle me. After I first installed the Runcore SSD but before I reformatted the disc to a GUID partition, the overall score was 178.10 but because start-up time was 90 seconds, I followed the advice provided above and resolved the start-up issue. But now the overall xbench score has reduced to 153.13 from the 178.1 score right after the initial upgrade.
The only other xbench score that has lowered is the UI Test (215.12 to 202.35 which is lower than with the Apple SSD).
I don't want to get too retentive over the xbench scores, but this puzzles me.