after seeing andy g's cooler ( the thing is huge) i did think the bigger the cooler the better
Bigger will mean more pressure drop so more lag!
more to do with quality of the core rather than overall size.
and the most important factor if the air is actually getting to the cooler and out at the right speed.
too slow and you will have a higher act as the air passing through the cooler is not getting enough cooling
too quick and then the air will also get hot.