What's the best holesaw for GRP (acrylic bath and GRP header tank)?

I'm building up a set of the Bosch holesaws but I'm worried they may either
chip GRP or the GRP will destroy the saw teeth. Are they OK or would a grit
edged one be better, eg:

http://www.toolstation.com/shop/Powe.../sd1530/p73155

or would one of these be better:

http://www.screwfix.com/prods/43887/...n-Holesaw-20mm

?

I have to ask because in both cases I cannot afford *any* mistakes(!)

Cheers

Tim