Those profiles have lower voltages than stock, their only differece is that each has a lower voltage (for each frequency than the previous one).
Lower voltages mean less power consumed by the cpu (you know that P = V*I, don't you?), and so, lower cpu temperature which reduces the risk of damage and aging of the cpu, and a expected longer battery life.
They are also deprecated for kernel power 49 and variants. The reason is that the cpu has a feature called SmartReflex (google it) which should adjust the voltages dinamically to the minimum possible to get the best power savings. Unfortunately, Nokia didn't implement correctly the driver for SR and it caused inestability and random reboots, so Nokia finally disabled SR leaving our devices with less than optimal voltage profiles, but stable.
Our dear TMO member Freemangordon realized that and took the work of reading TI's documents, did the right calculations and put them in the SR driver for kp49, correcting also the overclocking frequencies in the process.
So with kp49 and variants, the set of OC frequencies is different, and SR no longer causes inestability (on most devices at least, although there are a few reports of inestability and probably kp50 will have revised calculations), so it is better to enable SR and let the device calculate it best voltages. There is also a new overclocking profile "dsp" by Freemangordon, which has SR enabled, the new corrected frequencies and the optimum dsp overclocking for the new feature of recording at 720p, also kindly brought to us from the N9 by Freemangordon.