I have a Push-Pull on my CoolerMaster hyper 212 EVO CPU Cooler. In my case it does a very good job of keeping my 3700x processor (TDP rated 65 Watts with Maximum Operating Temp of 95c) below 70c all the time under any loads.
I see Three advantages in having a Push-Pull Configuration:
1- Slightly better cooling effect of the CPU Cooler
2- Helps increase Air Circulation inside the PC case by having an extra fan inside the case.
3- If one CPU Cooler fan fails, at least you have the second one to prevent your processor from overheating.
Now in your case, if you have a small PC case where the second fan may not have enough room to operate properly in moving air through the CPU Cooler then I would suggest using one CPU Cooler Fan but replace it with a High CFM fan that rotates around 4000 - 5000 RPM. That would force a higher flow of air through the CPU Cooler heat sink.