For "everyday use" you can't notice a difference between the two.
But given that the C300's have better random performance and that RAID0 will help increase overall bandwidth for sequential, I'd imagine that 2x C300s in R0 would be "Faster" than 2x M4s in R0.
I dont know about TRIM, maybe maybe not, I used to own an OCZ Revo and it did NOT have trim. It slowed down over time for me. So I sold it and went back to black drives.
I guess I need to know: Can you just wipe your drives (reformat, maybe a low level format or something) and start over to correct the performance issue relating to degraded drives (lacking TRIM), or is the degradation permanent on the drives? (Yes, I'm definitely new to this)