I have had stock, 20x10x9 razr2, and stock yfz tires. Razr2s are way too stiff for a bike as light as the 250, and they robbed quite a bit of power. Also hated them on my yfz.
The stock yfz tires work extremely well and are light(4 ply) so no loss of power. Being a radial, they handle an ride awesome. But Don't do the best if you ride in a lot of sloppy mud. Highly recommended.
I'm very biased to any holeshot, the next set to go on my wifes will be either original 4ply holeshots or holeshot SRs, in a 20x10x9