The thing about delrin is that it wears like a rock. Strong and smooth and rigid. In my limited experience PET is softer, as is HDPE. Those two are also less rigid, which might me a problem, might not. (I printed some spring clips in PET; they work nicely). http://www.ulsinc.com/materials-library/materials/pet/ says it produces flammable vapor when laser-cut and should be watched carefully. Ditto HDPE and my personal favorite, UMHW PE (ulsinc.com’s searchable library is pretty cool, btw).
And apparently PE can’t be easily engraved, because you just get a pool of melted plastic that re-solidifies.