Unusually for me, I'm just gonna let the facts speak for themselves...
In SL the smallest prim is 0.01 x 0.01x 0.01m, in IW it's 0.001x 0.001x 0.001m
In SL you can hollow out a prim 95%, in IW it's 99%.
In SL the largest prim is 10x10x10m, in IW it's 128x128x128m (256x256x256 if you use the Impudence viewer.)
In SL you can link prims upto 32 meters apart, in IW you can link upto 256 meters apart.
in SL a mainland prim costs 13 cents per month, in IW a mainland prim costs 2 cents per month.
Time for the Boys to improve the facilities?
InWorldz wins currently, hands down.