One unexpected, yet statistically proven benefit of three-reel slots is that they generally (not always, but mostly) have a higher high frequency.
http://005.wdgame88.com/forum.php?mod=viewthread&tid=5398&extra=
http://mirosovak.edoras.cz/viewtopic.php?f=3&t=567687
http://biopharmamash.com/viewtopic.php?t=1792984
http://eporady.starostwo.ketrzyn.pl/viewtopic.php?f=4&t=94667
http://mirosovak.edoras.cz/viewtopic.php?f=3&t=568421
http://www.lada-xray.net/showthread.php?p=213703#post213703
https://www.ww2.site/forum/viewtopic.php?t=336159
https://www.legacy-france.org/index.php?showtopic=24635
https://wietmarkt.nl/viewtopic.php?t=574118
https://gravatar.com/virtualsoul3c1679417e