I've played games where you choose the route as if it were episodes (DiaLovers has no common route), with a short common route that branches into each character's route or with a long common route with slight variations and you only get into a certain character halfway through the game, and honestly it depends.
If the game is untranslated having a long common route is quite tiring since I have to translate everything to see if there are any different scenes (ex. Juuzaengi doesn't skip everything you have already seen if there is a slight dialogue difference, which makes sense since the conclusion of that scene is different, but I end up rereading stuff I've already translated and sometimes get confused, but seeing how choosing a different option can lead to a different outcome in a battle can be quite rewarding).
However having a shorter common route canlead to more time with the chosen LI and thus better character development, so I do prefer that