I agree, there is extra information needed for full context. Shimano has typically done a good job at spacing freewheels and cassettes, of any count, well. Type of terrain--all flat, mix, punchy hills, brutal climbs, etc--is also important to know.

If you have a mix of flat and brutal climbs, that can tax a super wide range 8-speed cassette (and thus rider) more than it would 10- or 11-speeds because the jumps are larger than they would be.

If you're running the flats for a lot of these rides with only mild hills, this is where the genius of Campagnolo gearing is really nice. So many of their 8- and 9-speed cassettes are 13-26, which is madness for Seattle riding as you need gears above and below that range. But for rolling hills and flats, that close a spacing is dynamite and lets you perfectly tailor your cadence to the road and headwinds. If you find yourself at the fast/small end of the cassette when riding with your friends, that's where a couple teeth jump can make a big difference in your cadence, potentially for the worse as a jump may be too large. Are you a spinner or a masher or in the middle?

You state under your avatar that you have what you believe to be a 1989 Cannondale SR400. If it came with Shimano 600 tricolor, it's an SR800. A picture and a serial number will confirm everything. If it is an SR800, I have the crit geometry of that, and they move very well. A picture (we love pictures--show off your ride, man!) would also tell us if there could be any fitment issues (getting power down is key) or out-of-the-norm setup. Heavy wheels? Heavy tires? Tires at too low a PSI? We just want to help! Really, though, show us your bike. We're here for the pretty, shiny things.