Synthetic is better than mineral in almost every way, but costs more.
However if you don't have a high performance or exotic engine, or a known sludger, or sees severe service, or spends its life near the Artic circle, mineral oil will do just fine.
More important perhaps is using the correct viscosity.
My last two cars went 140k miles on 5-30 mineral oil with no sludge.
This one? Synthetic 0w-30 or 40 all the way.
Rule #1 with me is when I buy a used car, all the vital fluids get changed. This one was an exception as it was under the 4yr/50k warranty.