From all accounts the XR400 is fantastic for a small dual sport, tough and reliable, with big tanks available, but it is kickstart only. They have just stopped selling them in Australia where they were the most popular off road bike for a long time. XR650L is solid, heavier and taller with electric start and not as capable off road as the lighter XR400. Depends what you are using it for. I find 250's great in the bush proper but not powerful enough on the highway if you are trying to get along, thats not to say you cant do it. Ride them and see which one suits.
Close to Antarctica and a long way from reality