If you're gonna buy one of these two bikes, go with the 400. The extra power will be nice, considering you're 205lbs, and could be riding it in power robbing sand. Physically, there isn't really that much of a difference between the two.
Like you I was torn between the two sizes on my Suzuki DRZ. 250 and 400. I weigh 215 and am about 5 ft 10. I chose the 400cc and I am REALLY glad I did. The 250 would not have been enough for me. I was told by several people when trying to make my decision that I would love the 250 for 2-3 months then I would have wished for the 400.
I say go with the 400. You control the throttle yourself. 400 has power but it is a smooth power that is more than controllable. Great bike the XR 400 so you will be happy I am sure. 250 is great but just to small for people about our size. Some may disagree but the majority will say to get the 400 I am guessing :D
Good luck and try to ride them somewhere if you can, that will aid in the decision making process alot.
PS: I think there is only 17 lbs difference in weight between the 250 and 400.