A 92mm or 80mm fan would make no difference in temp if both are running at the same airflow. The increase in blade area is so small as to be virtually insignificant, especially at lower rpm. Let's put it this way: The Mini is a very good cooler, almost regardless of what fan you put on it, when you consider overall airflow/performance. It was not mentioned in the review, but you could even clip a 120mm fan if you leave the first 2 ram slots free. You can easily see how.
Running a larger fan at the same airflow isn't the question. The question is how much more airflow do you get and what is the effect on Â°C/W when you run a medium to low speed 92mm fan on the mini?
If you aren't going fanless and you are using speedfan or another fan control method that is variable you would want to know how effective extra airflow would be so you can decide how fast to run the fan under load. At idle it is simple. And of course you want to know if it is worth the time and money to make the upgrade vs whatever heatsink you are currently using.
According to article695-page2.html#nexus
a 120mm fan can approach 50 CFM at a reasonable noise level. article720-page2.html#nexus
gives us a 92mm fan that can approach 30 CFM at a similar noise level and the Fander below it shows that you can get to around 35 CFM near the noise level of the 120mm fan. The 80mm reference fan won't do more than 22 CFM and we don't have apples to apples data for the 80mm fan included with the mini (thought it is stated as 25CFM on the scythe web site).
So given that I would use the Ninja Mini with a fan controller that will automate fan speed changes I want to know how well it cools with more airflow than the 80mm fan can supply. What happens at 30, 35, and 40 CFM?
I might just bite the bullet and try it myself but for the sake of the SPCR community I'll ask the question that so many others will think but not bother to sign up for an account or even just login to ask.