Folks,
I hate to get mixed up in this, because some of the points are ephemeral, and thus can be argued back and forth until the bovines return.
It boils down this way. IF you dive on nitrox and use air tables, you are "slightly" safer, in terms of statistics. The percentage change is minute, however, and in the end not significant. I am sure that UP and Jon at least are well aware of this, since they have so stated previously in other posts.
The assumption is, of course, that if you go to a particular depth on nitrox, but only stay as long as you would if you were on air, you will have absorbed less nitrogen, because there is less of it in the mix.
IF you use nitrox, and nitrox tables (or wet-computer), you will be able to stay longer at a particular depth because you are NOT absorbing as much nitrogen (there is less of it in the mix).
Most folks dive on either NOAA NITROX I (NN32), at 32% oxygen, which gives you a Maximum Operating Depth of 130 fsw, or on NOAA NITROX II (NN36), at 36% oxygen, which gives you a MOD of 110 fsw.
Either way, if you use the PADI Nitrox tables, or a computer set to your mix, it is a simple process.
The only other thing to watch is your oxygen exposure. You use a CNS chart to run your oxygen clock, and for extended exposure to high oxygen concentrations, such as in repetitive technical diving, you run an OTU table to check long term (i.e. whole body, or pulmonary) exposure.
In the normal run of the mill recreational diving, neither one is much of a problem.
There is anecdotal evidence that, even running Nitrox on Nitrox tables, at the end of the day, you just feel better!
Take your pick!
P.S.--If you use the standard mixes, none of your equipment needs changing in any way, EXCEPT......
if your shop blends Nitrox through the Partial Pressure method, your TANK AND TANK VALVE needs to be cleaned, o-ringed, and lubed for oxygen service. This is because those items will see 100% oxygen at high pressure. The rest, once the mixing is done will not.