Not sure what your asking.

For my money stat points into STR yes, since one right side piece is more than all the stat allocation (35 points Vs 40 for a right side piece)

Having different sets for different occasions is always good.

Mostly I use Slaying right side .. Its very rare that I'll swap to Fending right side, the healers have to be pretty bad or if I'm MTing A4 in a PUG I'll swap to Fending, other than that I'm always in Slaying.

Slaying gives me near 15K Hp .. no reason to use Fending for 95%+ of the game IMO.