smallRNA v1.5 versus TruSEQ

[Fiji_surf]

Hi all,

I have sequenced the same small RNA sample using v1.5 or TruSEQ.
As one might expect the data was overall similar, but what I have noticed is that RNAs that are 17-19 bp long (trimmed versions of mature microRNAs) were detected by v1.5 , but not by TruSEQ.

So, I was wondering whether anybody knows the difference between these procedures that can explain the bias?

Thanks.