Aftermarket fan / genuine fan

Hello!
I was wondering if any of you know if there is much of a difference between buying an aftermarket fan for my radiator or a genuine one. I have a patrol 2.8 diesel 1998 and I've heard they tend to overheat and right now it has a non-genuine fan that activates with a switch, I've been recommended to put a regular one back on but I don't know if it's worth the extra money for the genuine one.
Sorry if it's a bit of a noob question, It's the best car that I've bought and I'm learning :)
Thanks!

Hi mate, if someone has removed the Viscous fan in favour of a Thermo Fan and electric switch then 100% the Viscous is a better setup. If the car getting hot now?

Thanks for the reply! It's not getting hot now but I live in Denmark (WA) so absolutely nothing gets hot in here at the moment hahaha. Planing to go up north tho so I want to make sure that the cooling system is in good condition.

you will probably find they removed the viscus hub and fan because it was shot, and was a cheaper fix to fit the thermo fans

in all honesty, the original setup is the best for these
if you have a GOOD mechanic - not just a spanner spinner - get them to get the viscus hub & fan from Mr Nissan - costs, but works better than aftermarket (I have tried the "cheaper" aftermarket, then had to spend more on original parts for my cooling system)
and while they are there, get them to pull the radiator out and back flush it, as well as spraying from engine side out - to clean it out, also do the aircon evap cooler in situ from the engine side
you will be amazed at the amount of crud that will come out
once that is done, you "should" have many happy travels without radiator problems - unless there is something else wrong somewhere

Go with OEM fan. Buy once cry once.