I know this question was asked awhile ago but its a great question. Today many people are going the less expensive route and using a typical 3 cm paver for pool coping (which is about 1 1/4" - 1 1/2" thick). Reason behind it, is that it is easily available and in stock, not as heavy or as difficult to cut and cost effective. The next standard upgrade is 5 cm or 2" thick, which most stone places consider coping. If you compare that to a poured in place concrete deck that has kooldeck over it - that is usually poured 3"-4" - the paver can seem thinner and cheaper looking. And there are other types of coping out there such as precast concrete coping or brick paver coping - those tend to run about 2" to 2 1/4". However a good stone distributor can get you travertine coping or even various other stone materials cut thicker, it would just require you ordering it to your specifications. We like to use at least 7 cm or 3" coping wherever possible - we think it makes the coping look more substantial and side of the pool look more to scale with the size of the pool. The minimum we use is 5cm. So your decision of what to use would be based on what look you like, perhaps what's available in your area and as always, your budget. If you have any questions about the various types and advantages and disadvantages, let us know.