not too sure why you're posting in forum feedback area for mt related questions. same with all your other new threads these have likely been answered already.
http://wmexpressway.net/index.php?showforum=5 < that is the main section for wmmt related topics
http://wmexpressway.net/index.php?showtopic=34404 here's the place for mt questions.
but anyway to answer your question the discard obviously saves you 20 games so why not take that option? unless you really wanted to play those first 20 story for some reason. those 20 games you saved can go towards money for VS, ghost or even halfway tuning a new discard of another car.
This post has been edited by WRX22B1998 on Aug 11 2018, 07:38 PM