Hi, I'm going to go through my experiences using two different hybrid coolers; the MSI Dragon Gaming Series hybrid cooler, and the Corsair H75 hybrid cooler. The MSI cooler is using the stock 120mm unbranded fan included with it, the Corsair cooler is using an SP120 infront of the rad and an AF120 behind it.
These two represent the top and bottom end (IMO) for hybrid coolers using 120mm rads. I think 120mm versions of these coolers are going to be more popular, since they fit in a wider variety of cases and are much less space reliant.
I will mainly be focussing on my experiences with these units in an exhaust vs intake test, to see what kind of temps we get using each in a Cooler Master Silencio 352 noise-optimised case. I think this is a pretty good case for this test, since it's small size and it's noise-insulation makes it pretty difficult to cool efficiently.
Idle temps are taken with 5-7% processor usage, load temps are taken during a Prime95 CPU torture test, with all 4 cores of my i5 reading 100% usage (Unrealistic for normal use, but the best extreme for testing cooling)
I used my main rig (in my sig) to take these readings, I have one constant SP120 intake in the front and one constant AF120 exhaust in the back.
Test 1: MSI Gaming Series Cooler (1x120MM fan) - Intake
Not bad, well not that
Test 2: MSI Gaming Series Cooler (1x120MM fan) - Exhaust
Still not terrible
but worse than being used as an intake.
Test: 3: Corsair H75 (2x120MM fans in push pull) - Intake
Looking much better with the corsair here.
Test 4: Corsair H75 (2x120MM fans in push pull) - Exhaust
Idle: 39-42C and fluctuating between
Load: 69C fluctuating up to 70 but hovering around there.
I think then, from these results, that for a single 120mm rad setup, having it as an intake is the best way. Of course, you will need a seperate unradiator-ed intake to provide cool air for your GPU, and at least one exhaust fan in the back to get rid of the hot air coming out of the rad.
I think the higher temps when running it as an exhaust is due to the other heat sources in the case; meaning that already warm air is being drawn through the rad and not really doing much cooling to the coolant.
Bare in mind that this is only my experience and is probably specific to noise-optomised cases or perhaps more broadly all mATX cases due to the lesser inner space and thus the heat being more concentrated.
In conclusion, if you have a small case and can't fit a 240mm rad in there, mount your 120 rad as an intake and try to create positive pressure (more intake than exhaust).
Just my two cents!