yeah, I became obsessed with all this at the start of the year and bought some 180mm cranks.
I have an 89.5cm inseam (35.23"😉, and there's absolutely no way I could use anything longer than 180! Some of those formulas would have me using 193mm cranks, which is totally rediculous.
I do like the 180s (I had 175s), but i'm still not 100% 'sold' on them. Don't get 190s.
How tall are you, and what's your inseam?
What is not really expanded upon on those sites is the dramatic effect that longer cranks have on seat height (lower) and seat "reach" (forward postion). The problem is, that while there may be an increase in leverage, this could be offset by being in a lower/weaker position. Even though I increased my crank length by 5mm, I've found that I've had to lower my seat about 7mm. This means that, compared to the 175s, my knees are coming up approx an extra 12mm higher, relative to my hips through the top of the pedal stroke.
I also found I was reaching forward a bit too much -- so much so that I've bought a smaller frame to try to 'get over' the cranks.
Don't get long cranks if you are a sprinter type of rider.
In my opinion, the Kirby Palm site is not worth reading, and Lennard Zinn has generalized a bit from his own experiences -- he's very tall. Andrew Bradley's site is probably the best (http://www.cranklength.info/): even though his preference is for longer cranks, he offers a stack of balanced info.
having said all that, don't freak out too much about it; a 6ft guy using 180s is probably just like all those 5'6" guys out there using 170s :p
here's a very long thread on crank length with a lot of anecdotes
http://www.cyclingforums.com/showthread.php?t=11281
You'll find others if you do a 'title only' search for 'length' or 'crank'
