We have "
DynaProof" (poly/cotton) 12oz on the roof and awning and (either) 10 or 8 for the walls (can't remember which sorry). Whilst it does feel nice and thick, it is suprisingly light (although alot of it would get heavy of course), and depending on the colour will let a certain amount of light through.
I believe the only real difference you will find is that
Ripstop has a distinct "line" going through it.
Both work on the same waterproof and mould proof properties ... so I guess it's just what you prefer. Don't know how they compare $ wise though.
Kit_e