Both have a good feel vibe and will make you smile. Both won't make you cry and don't contain serious themes. Different stories,same warm feeling inside.
Both FLs are spirited and a bit silly, and enter the palace disguised as eunuchs. The emperor discovers or knows their secret and falls in love with them.
Both of them are about high school students who travel back in time! The male lead in this drama is mistaken as a vassal while the female lead in Splash Splash LOVE is mistaken as an eunuch. Both dramas are light and sweet!
They are both time traveler from modern day to help out the King in the past.
Although both are kinda over the top but the Journey to Tang is a bit (very) unrealistic compared to Splash x2 Love. They are both fun and amusing for a short movie/drama~