Which type of fan system do miners here at Bitcoin talk prefer? I myself, have only used 1 blower and 1 dual fan card. I find the blower stays cooler, the dual fan heats up all the other components next to it. If I put my blower on top slot and dual fan on the bottom the blower gets to hot
but I found if I put the blower on bottom and the dual on top, the dual fans actually cool down my blower into the low 60 c
my rx 580 is running at 72 c and my msi 170 aero running at 60c, I have to keep my case open if not the dual fan makes the whole case hot.
It depends on how you're arranging your cards, your case, and airflow setup. In an open air rig, multi-fan cards (2, 3 fans) do a much better job at heat dispersion than a blower. However, if you're running inside a standard ATX tower, blowers are generally more efficient because they push the hot air out the back of the case instead of recirculating it back into the case. The recirculation can be more efficient if your tower case has ample case fans and can get the heat out (disperses faster), but it makes sense why your blower is more efficient in your case (saying it is "on top" leads me to believe you're using an ATX tower).
In my gaming computer I have 2x 1080Ti blowers which stays much cooler in its environment. However, I much prefer any other card (noise and heat) in my open air rigs in the basement.