i have been riding for about 10 months and i am getting to the point where i want a faster/more powerful bike. im 21 years old, 5'11", 175 pounds, and riding a 2003 yz125. i live in arizona and mostly ride trails and in the desert. im looking at a 2003 or newer used yz250 or yz250f i plan to continue to ride mostly in the desert and start taking trips to mexico to ride in the sand dunes and maybe go to the track a few times a year. in your guys opinion which bike should i go with (ive never been on a four stroke) but have heard they are more well suited for trail riding. so which one? thanks for the help