What the Pressure spec of a fan means is that it CAN provide some air flow against a backpressure LESS than that. The fan gives its max air FLOW at max speed against NO backpressure, and less flow as backpressure increases, until at and above the PRESSURE rating you get virtually NO air flow. So, looking at the specs you cited, the two Noctua fans will produce VERY little actual air flow if the backpressure (resistance to air flow through the rad fins) exceeds 2.5 mm water, whereas under those same conditions the ML120 will still blow perhaps 40% of it max airflow rating. This suggests that the Noctua fans you checked out were not really designed for use with tightly-spaced fins, although they are rated higher for max backpressure than fans optimized solely for free-air case ventilation situations. If you really want the high Pressure rating, look further in the Noctua line, because thy have SOME models that exceed 4 mm water pressure. The tough part of this, of course, is that you do NOT know what backpressure the rad you have does present to airflow.
You post title asks a different question, though: Will you see a big change in TEMPERATURE?
Generally, no, BUT sometimes yes. How's that for confusion? We must start by recognizing exactly what an automatic fan speed control system does. It really is a TEMPERATURE control system. For the CPU, it watches carefully the actual temperature inside the CPU chip according to a sensor built into the chip. Pre-programmed into the mobo BIOS is the desired target temperature for that particular chip type. The control system manipulates the speed of the CPU cooling fan to whatever it takes to keep the TEMPERATURE on target. It is not trying to control to a speed target; it is using speed to achieve a temperature target. So if you change the fans involved, with NO change of temperature target, the fan SPEED will be adjusted, but the internal CPU TEMPERATURE will be kept to the same target or very close. Where you DO see a difference is when the system is being used heavily and generating a LOT of heat. In those situations, a poorer-performing fan will end up running at top speed and still not able to keep the temp down as well as a better fan that has more reserve cooling capacity. So better fans give you more ability to work really hard without overheating.