Originally Posted by DirtJack
Pom, I've never ridden a 250, but other than the points made by WarriorPrince, I would expect there might be (quite) a few hp as the most notable difference.
DirtJack does make a very good point.
In many "for sale" ads, that I see for used KTM "250" two-strokes, you will see the, "bike has 300 kit" words in the ad.
EDIT: Pom, After re-reading many of the last posts in this thread, I also had the opportunity to re-read mine (and yours). I hope my "well-informed" observation was not taken the wrong way. I actually meant it quite literally. I have been riding and wrenching on bikes for years. However, there are many gentlemen, in this thread, who have ten-times the experience with these 300's that I do. All I can offer is my very limited, and very humble, opinion.