Which SERP tool is the most accurate?

I have found that while many people say to use many tools (and I admit I do so), I always keep the stats separate, as it is the ratio of the data provided and not the actual numbers that I use. If KW#1 has better data than KW#2 and this is accurate according to #1/#2 compiled niche averages, then #1 replaces #2, to hell with the exact #s. I am not going to refuse 100 mth traffic, if it is more profitable statistically than anything else I have in the DB.

The only accurate data you can have about search traffic is to get #1 on Google and check your stats by keyword referrers. Trends in their algorithms however is another matter. For That I would suggest KSS found right here in the BHW forums.