Mr Carcharodon
Contributor
There was a comparison of NDL v. dive time for repetitive dives on different computers at deco.org. Their main website may not still be up but they have a FTP site. Also in Karl Huggins course on decompression from Wrigley Marine Sciences (you can find it on the web too) you will find another comparison. Some algorithms, like RGBM, have substantial penalties for short surface intervals, rapid ascents or reverse profile dives. In general you will see larger differences when those conditions occur. Also you will see large differences in ~35-50 fsw range where the slope of the curve is steep. Finally of course VPM will give you credit for deep stops if you are over threshold values but the Buhlman based computers will penalize you for those stops.
Oh and the previous poster is right about UWTEC having a penalty for cold water. I have personally seen that result in a 20 minute discrepancy between computers on a repetitive dive. That penalty in particular seems ill advised since presumably the computer does not know what the diver is doing for exposure protection. Large differences computer to computer make it hard to keep a team all on the same plan. So as usual it is better to have a plan before getting into the water and to have the computer in gauge mode.
Oh and the previous poster is right about UWTEC having a penalty for cold water. I have personally seen that result in a 20 minute discrepancy between computers on a repetitive dive. That penalty in particular seems ill advised since presumably the computer does not know what the diver is doing for exposure protection. Large differences computer to computer make it hard to keep a team all on the same plan. So as usual it is better to have a plan before getting into the water and to have the computer in gauge mode.