Hello Mee,
There are different variables to consider here since you have different configurations not only in the RAID modes but in hardware specifications.
Was the performance degrading or always like this since the fresh Windows* installation? I see you have different brands of SSDs. Are the SSDs specifications regarding transfer rate similar? I did not fully understand, are they both Intel® P67 Chipset?
It is possible the SATA controller is not providing TRIM to the SSDs in RAID. TRIM in RAID is supported starting with Intel® Z77 Chipsets.
If you had identical systems it would be easier to compare the different RAID modes but still, for a striped array the booting time is very slow, it should be way less time. Hence, my thinking tells me that there is something related to the SSDs (in RAID) causing the issue. I may suggest testing with a single standalone SSD if possible.
