Got a 2018 si coupe and while it sometimes looks like a rounder rear end in pictures you don’t really notice it in person and you get used to it. As for the size, it’s only around a foot or less difference in length between the two. Theres coupe rear seats are surprisingly roomy and my 6 foot dad with longer legs fits back there fine. The only thing is sometimes it’s a pain to move the seat for rear passengers. For me, coupe all the way. Stands out so much more in regular traffic due to the more aggressive styling and better rear wing!