well, the first question is not a new one - I run 165s for streettrack. makes cornering easier. More info here/stories here:
http://bikeforums.net/showthread.php...t=crank+length
http://bikeforums.net/showthread.php...t=crank+length

As far as 2 diff lengths on 2 diff bikes, I ran 180mm on my SS MTB and then had 165mm on the track. Yeah, I felt it. So I chose track. But not sure of the difference you feel and how that will effect the different rides.