I have tried these black poly strings.
MSV, Tornado, B5E, BHB7, and RPM Blast.
Tornado and RPM lose tension fast.
They are all spin strings....depend on your spin style and how do you like it.
B5E is the softest.
BHB7, Tornado, and RPM are crispy.
Tornado and BHB7 have more power.
In my opinion, try and find one that is compatible with your racket and fit your playing style. I like RPM Blast 16G on the new APD 2013 from the 2nd hour to around the 10th hour after that it is losing its characteristics.