corsair 120gb ls

hi all i have 2 corsair 120gb ls not on raid

both on sata 0 and sata 1 wich is 6gb/s

i also have 1tb wd black

when i move file from my hdd to my ssd its around 80-100 mb/s

but when i move the same file between my ssd's its jumpin all over the place startin from 1-250 mb/s

its large file

on ssd benchmarks utilities i get 450-490 transfer rate on both ssd's

any 1 knows why its happenin?