1.) Eun Ji as the female lead with similar personalities. Sassy girl who is bad at studying. And male lead being the one good at studying.
2.) Second male lead is the brother (or close friend) of male lead, making the male lead hesitate in love.
3.) Best friend of female lead also has similar personalities. N in Sassy Go Go and Hoya in Reply 1997. Both are quiet and shy, yet are the "wise" ones.
Will say that Reply 1997 generally has more content as well as twist and turns as compared to Sassy Go Go. But after you finished watching Reply 1997 and want more sass from Eun Ji, Sassy Go Go is a possible choice. Sassy Go Go has more fluttering moments though as the male lead is proactive than the one in Reply 1997.