Going to a higher gear ratio will give you better low end power while going to a lower gear ratio will give you higher top end speed. So it really it depends on what you are trying to accomplish, are you trying to beat more people off the line or are you looking for better highway speed/doing the time?
I went up 2 teeth on my CB450SC to an 18 tooth front sprocket, I use it for commuting and that gear ratio makes it so I can go 65 in 5th up the mountain roads and still use 6 as an overdrive/cruising gear. Before that my 6th gear was (and still is) to weak for going up mountain roads and my 5th gear was reving way too high at 65 so I would go 55 up the canyons. It isn't as fast off the line, but I wasn't winning races anyway, and I like the taller 1st gear.
I went down a tooth on my CBR600 it made my 1st gear about 5 mph shorter, but it gave me a lot better power coming out of the turns so even though my top speed was reduced a little bit, my times got faster on the track because of it.