i think its 350mm difference which doesnt seem alot but with the medium already near 5mtr that extra results in over hang in the long version in most parking spaces, a test drive including parking practise is a must if your not used to bigger vehicles. at only £200 more the Long offers so much more versatility but you have to be comfortable with it, try for an Extended test Drive, or maybe consider hiring one for the day as a lot of hire companies use them.