I agree with Fuzzy, if I was shooting for high 10's-low 11's I would you want more than 10 or 11 points of data and something in the range of 180-200 points of data is just perfect. Some say thats too much data but you don't have to get that granular if you don't want to but its sure nice to have if the car does something stupid and it only happens for a split second. So you wont have boost sensing, its not hard to make a peak and hold for your boost gauge and it costs nothing to glance over at the gauge at the tops of gears couple times during a run. DS doesn't run in windows, fine with me as I don't want to wait for windows to boot in the staging lanes anyway, dos boots in no time. Don't get me wrong, I feel both products are fine products and I know Ken has put a lot of time, effort and customer service into his product.
Now for a quick note on scanmaster, when I loaned DS to a friend w/ one and used both during 1/4 mile racing, after each run when knock occured, DS always reported more knock than the SM did and the only thing we could figure was because of the slow data rate, it was missing reported knock...NOT good. Now SM was usually pretty close, usually within 1-2 degrees lower than what was reported by DS but if your tuning at a max level of 5 degrees(not condoned) and your actually getting 7.....you get the idea.
The ecm connector can sometimes cause problems with DS as its very sensitive to cleanliness and depth of connection but once you get it set your good.
Just my .02
My choice was lots of data and DS and I'd recommend it to anyone looking for a tuning tool. I also have a caspers knock gauge for when DS isn't in the car.