Until a couple years ago Sixt used to have the best and most competitive rates. Be aware no longer is that the case. I used to book almost exclusively from them but now always shop around. You can get Enterprise for half the rate. Also Sixt now has second driver charge, one way rental charge, Class-bruch and tire insurance. In the old days wind-shields and tires were covered, now Sixt will charge you extra for that as well. Even though I am their Platinum member I stay away from renting from Sixt unless for weekend rates.