I have both Rotozip and Porsadrill bits. For cutting clean holes for pipes the Porsadrill is first class. For cutting those nasty odd curves (e.g. if you cut around toilet and sink plinth bases) the Rotozip is the tool to use. Both tool bits require care to get the best out of them. I burnt out my Porsadrill 16mm bit cutting through a hard floor tile - my fault probably for drilling too fast! The Rotozip bits are prone to breakage if you dont take care to drill in a sawing motion. Either way - not following the manufacturers guides is expensive!