Hey I also string with a wise tension head with constant pull and I tried Luxilon ALU Power on the 99s and it only lasted me like 5 hours. That's the first time I've ever snapped a poly and I'm coming from an APDGT. I'm also testing out some of the 4G stuff like the 16g and 15g. The only thing I'm concerned with is that I might generate a lot less spin with a 15g.
I would go for the extra durability. The string bed is already so open that the ball will be sinking sufficiently deep into the string bed with the 1.41. Should be a minimal difference in spin potential.